This work was supported by the Natural Sciences and Engineering Council of Canada and the Ontario Ministry of Research and Innovation.

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The authors declare that they have no competing financial interests.

הניתוח של חלבוני קושרי כובע בתאים אנושיים חשופים לתנאי חמצן פיסיולוגיים יכול לאפשר זיהוי של גורמי ייזום תרגום רומן מוסדר חמצן. הזיקה של הגורמים הללו עבור המכסה &#39;5 של mRNA או חלבונים הקשורים כובע אחרים ניתן למדוד את עוצמת הקשר שלהם אל מ 7 GTP צמודים חרוזי Agarose. אזהר?...

שליטה Translational מתגלה צעד חשוב לא פחות לרגולציה תעתיק בביטוי הגנים, במיוחד בתקופות של מתח הסלולר 1. מוקד שליטת תרגום הוא צעד שער הגבלת חניכה שבו הצעדים הראשונים של סינתזת חלבון לערב הכריכה של 4E גורם ייזום איקריוטיים (eIF4E) אל 7-methylguanosine (מ 7 GTP) 5 &#39;כובע של mRNAs 2 . eIF4E הוא חלק ממכלול trimeric בשם eIF4F הכולל eIF4A, גידול helicase RNA, eIF4G, חלבון פיגומים הנדרש לגיוס של גורמי תרגום אחרים ואת 40S הריבוזום 3. בתנאים פיסיולוגיים נורמלים, רוב mRNAs המכריע מתורגם באמצעות מנגנון כובע תלוי, אבל תחת תקופות של מתח הסלולר כ 10% של mRNAs האנושי מכילים 5 &#39;UTRs עלולה לאפשר תרגום עצמאי-כובע טכס חניכת 1,4. תרגום שווה תלויה כבר היסטורי נרדףמפוקפק עם eIF4F, לעומת זאת, וריאציות ספציפי לחץ של eIF4F הפכו נושאי טרנדים 5-8. מדגיש תאיים שונה לגרום לפעילות eIF4E צורך להדחיק באמצעות היעד היונק של rapamycin מורכבי 1 (mTORC1). קינאז זה הופך לקוי תחת לחץ, וכתוצאה מכך את הפעילות המוגברת של אחד היעדים שלה, 4E-חלבון מחייב (4E-BP). ללא פוספורילציה 4E-BP נקשר eIF4E וחוסם את יכולתה לקיים אינטראקציה עם eIF4G גורם לדיכוי של תרגום תלוי כובע 9,10. נקודה מעניינת היא homolog של eIF4E בשם eIF4E2 (או 4EHP) יש זיקה הרבה יותר נמוך עבור 4E-BP 11, אולי שמאפשר לו לחמוק הדחקה בתיווך מתח. ואכן, בתחילה לאפיין מדכא של התרגום בשל היעדר האינטראקציה עם eIF4G 12, eIF4E2 יוזם את התרגום של מאות mRNAs המכילים אלמנטים בתגובה היפוקסיה רנ&quot;א 3 שלהם &#39;UTR במהלך מתח היפוקסי 6,13. אני הפעלה זושעות מושגת באמצעות אינטראקציות עם eIF4G3, RNA חלבון מחייב מוטיב 4, והגורם היפוקסיה מושרה (HIF) 2α להוות מורכבים eIF4F חוסר חמצן, או eIF4F H 6,13. כתוצאה מדכאת בתנאים רגילים, eIF4E2 נקשר עם GIGYF2 ו ZNF598 14. מתחמים אלה היו, בין שאר, שזוהו באמצעות שרפי זיקת GTP מ 7 Agarose צמודים. השיטה הקלאסית זה 15 הוא תקן בתחום התרגום והוא הטוב ביותר הנפוץ טכניקה לבודד מתחמי מחייב כובע לנתץ ו במבחנה מחייב מבחני 16-19. כמו מכונות תרגום תלוי כובע מתגלה גמישות להתאמה עם חלקים בין-שינוי 6-8,13, שיטה זו היא כלי רב עצמה כדי לזהות חלבוני כובע מחייב רומן במהירות מעורב תגובת הלחץ. יתר על כן, וריאציות eIF4F עשויות להיות השלכות רחבות כמערכות מודל מספר איקריוטיים להופיע להשתמש homolog eIF4E2 לתגובות מתח כזהכמו א thaliana 20, ס Pombe 21, ד melanogaster 22, ו- C. elegans 23. הראיות עולה כי שינויים eIF4F לא יכול להיות מוגבל למצבי לחץ, אבל להיות מעורבים בפיזיולוגיה נורמלי 24. אספקת חמצן לרקמות (בקצוות נימי) או בתוך רקמות (נמדד באמצעות microelectrodes) נע בין 2-6% במוח 25, 3-12% בתוך הריאות 26, 3.5-6% במעי 27, 4% ב הכבד 28, 7-12% בכליה 29, 4% בשריר 30, ו 6-7% ב מח עצם 31. תאי המיטוכונדריה מכילים פחות מ -1.3% חמצן 32. ערכים אלה הם הרבה יותר קרובים היפוקסיה מאשר באוויר הסביבה שבה תאים בתרבית באופן שגרתי. הדבר מצביע על כך מה בעבר נחשבו כמו תהליכים תאיים ספציפי היפוקסיה עשויים להיות רלוונטיים בסביבה פיזיולוגית. מעניין, eIF4F ו eIF4F H </sup&gt; להשתתף באופן פעיל בייזום התרגום של ברכות או כיתות נפרדות של mRNAs בכמה שורות תאים אנושיות שונות נחשפות לחמצן פיסיולוגי או &quot;physioxia&quot; 24. חמצן נמוך גם דוחפת להתפתחות תקינה של העובר 33 ותאי בדרך כלל יש שיעורי התפשטות גבוה, תוחלת החיים ארוכה יותר, פחות נזק בדנ&quot;א ותגובות הלחץ הכללי פחות physioxia 34. לכן, eIF4F H עשויה גורם מפתח בביטוי של גנים בוחרים בתנאים פיסיולוגיים. כאן, אנו מספקים פרוטוקול לתאי תרבות בתנאי חמצן פיסיולוגיים קבועים או במגוון משתנה דינמי כי סביר יותר נציג microenvironments רקמות. אחד היתרונות של שיטה זו הוא כי התאים lysed בתוך תחנת עבודה היפוקסיה. לא לעתים קרובות ברור כיצד מעבר מתרבות תא היפוקסי תמוגה התא מתבצע פרוטוקולים אחרים. תאים הם לעתים קרובות להסיר תחילה מן חממת היפוקסיה קטנה להיותקדמי תמוגה, אבל לחשיפה זו חמצן יכולה להשפיע הביוכימיים כתגובה הסלולר לחמצן היא מהירה (אחד או שתיים דקות) 35. חלבוני כובע מחייב מסוימים דורשים אינטראקציות עם בסיס שני או יכולים hydrolyze GTP מ 7, ולכן חלק interactors הכובע עלול לרדת לטמיון בתהליך הטיהור. Agarose-צמוד אנלוגים כובע עמיד enzymatically ניתן להחליף בפרוטוקול זה. היכרות עם הפעילות ורכב eIF4F H וריאציות אחרות של eIF4F באמצעות השיטה המתוארת כאן שתשפוך אור על מנגנוני ביטוי הגנים המורכבים שתאיים לנצל במהלך מצבים פיסיולוגיים או תגובות דחק.

<table><tbody><tr><td>&amp;gamma;-aminophenyl-m&lt;sup&gt;7&lt;/sup&gt;GTP agarose C&lt;sub&gt;10&lt;/sub&gt;-linked beads</td><td>Jena Bioscience</td><td>AC-1555</td><td>Agarose-linked m&lt;sup&gt;7&lt;/sup&gt;GTP</td></tr><tr><td>100 mm culture dish</td><td>Corning</td><td>877222</td><td>10-cm culture dish</td></tr><tr><td>150 mm culture dish</td><td>Thermofisher</td><td>130183</td><td>15 cm culture dish</td></tr><tr><td>AEBSF Hydrochloride</td><td>ACROS Organics</td><td>A0356829</td><td>AEBSF</td></tr><tr><td>Agarose Beads</td><td>Jena Bioscience&amp;nbsp;</td><td>AC-0015</td><td>Agarose bead control</td></tr><tr><td>Bromophenol Blue</td><td>Fisher</td><td>BP112-25</td><td>Component of SDS-PAGE loading buffer</td></tr><tr><td>1.5 ml Centrifuge Tubes</td><td>FroggaBio</td><td>1210-00S</td><td>Used to centrifuge small volumes</td></tr><tr><td>15 ml Conical Centrifuge Tubes</td><td>Fisher</td><td>1495970C</td><td>Used in culturing primary cells</td></tr><tr><td>Defined trypsin inhibitor</td><td>Fisher</td><td>R007100</td><td>DTI</td></tr><tr><td>Dithiothreitol</td><td>Fisher</td><td>BP172-25</td><td>DTT</td></tr><tr><td>Epithelial cell medium (complete kit)</td><td>ScienCell</td><td>4101</td><td>Includes serum and growth factor supplements)</td></tr><tr><td>Glycerol</td><td>Fisher</td><td>BP229-1</td><td>Component of SDS-PAGE loading buffer</td></tr><tr><td>100 mM Guanosine 5&#039;-triphosphate, 1 ml</td><td>Jena Bioscience</td><td>272076-0251M</td><td>GTP</td></tr><tr><td>HCT116 colorectal carcinoma</td><td>ATCC</td><td>CCL-247</td><td>Human cancer cell line</td></tr><tr><td>Human renal proximal tubular epithelial cells</td><td>ATCC</td><td>PCS-400-010</td><td>HRPTEC</td></tr><tr><td>Hyclone DMEM/High Glucose</td><td>GE Life Sciences</td><td>SH30022.01</td><td>Standard media for human cell culture</td></tr><tr><td>Hyclone Penicillin-Streptomycin solution</td><td>GE Life Sciences</td><td>SV30010</td><td>Antibiotic component of DMEM</td></tr><tr><td>H35 HypOxystation</td><td>Hypoxygen</td><td>N/A</td><td>Hypoxia workstation</td></tr><tr><td>Igepal CA-630</td><td>MP Biomedicals</td><td>2198596</td><td>Detergent component of lysis buffer</td></tr><tr><td>Monopotassium phosphate</td><td>Fisher</td><td>P288-500</td><td>KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td></tr><tr><td>Potassium chloride</td><td>Fisher</td><td>P217-500</td><td>KCl</td></tr><tr><td>Magnesium chloride</td><td>Fisher</td><td>M33-500</td><td>MgCl&lt;sub&gt;2&lt;/sub&gt;</td></tr><tr><td>Sodium chloride</td><td>Fisher</td><td>BP358-10</td><td>NaCl</td></tr><tr><td>Sodium fluoride</td><td>Fisher</td><td>5299-100</td><td>NaF (phosphatase inhibitor component of lysis buffer)</td></tr><tr><td>Disodium phosphate</td><td>Fisher</td><td>5369-500</td><td>Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;</td></tr><tr><td>Premium Grade Fetal Bovine Serum</td><td>Seradigm</td><td>1500-500</td><td>FBS</td></tr><tr><td>Protease Inhibitor Cocktail (100x)</td><td>Cell Signalling</td><td>58715</td><td>Component of lysis buffer</td></tr><tr><td>Sodium Dodecyl Sulfate</td><td>Fisher</td><td>BP166-100</td><td>SDS</td></tr><tr><td>Sodium Orthovanadate</td><td>Sigma</td><td>56508</td><td>Na&lt;sub&gt;3&lt;/sub&gt;VO&lt;sub&gt;4&lt;/sub&gt;</td></tr><tr><td>Tris Base</td><td>Fisher</td><td>BP152-5</td><td>Component of buffers</td></tr><tr><td>0.05% Trypsin-EDTA (1x)</td><td>Life Technologies</td><td>2500-067</td><td>Trypsin used to detach adherent cells</td></tr></tbody></table>

analysis of cap-binding proteins in human cells exposed to physiological oxygen conditions

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex is by far the most common pathway to initiate protein synthesis in eukaryotic cells, but stress-specific variations of this complex are now emerging. Purifying cap-binding proteins with an affinity resin composed of Agarose-linked m7GTP (a 5' mRNA cap analog) is a useful tool to identify factors involved in the regulation of translation initiation. Hypoxia (low oxygen) is a cellular stress encountered during fetal development and tumor progression, and is highly dependent on translation regulation. Furthermore, it was recently reported that human adult organs have a lower oxygen content (physioxia 1-9% oxygen) that is closer to hypoxia than the ambient air where cells are routinely cultured. With the ongoing characterization of a hypoxic eIF4F complex (eIF4FH), there is increasing interest in understanding oxygen-dependent translation initiation through the 5' mRNA cap. We have recently developed a human cell culture method to analyze cap-binding proteins that are regulated by oxygen availability. This protocol emphasizes that cell culture and lysis be performed in a hypoxia workstation to eliminate exposure to oxygen. Cells must be incubated for at least 24 hr for the liquid media to equilibrate with the atmosphere within the workstation. To avoid this limitation, pre-conditioned media (de-oxygenated) can be added to cells if shorter time points are required. Certain cap-binding proteins require interactions with a second base or can hydrolyze the m7GTP, therefore some cap interactors may be missed in the purification process. Agarose-linked to enzymatically resistant cap analogs may be substituted in this protocol. This method allows the user to identify novel oxygen-regulated translation factors involved in cap-dependent translation.

ניתוח יכולת Cap-מחייב תגובה חמצן של eIF4E ו eIF4E2 בבית מ 7 טור GTP זיקה איורים 1 ו -2 מייצגים כתמים המערבי של טיהור זיקה מ 7 GTP טיפוסי של שני חלבונים כובע מחייב מרכזי בתגובה לתנ?...

Watch this Scientific Journal Video about Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions at JoVE.com

Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

ניתוח של חלבונים קושרי שווי בתאים אנושיים חשופים לתנאי חמצן פיזיולוגיים

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex ...

analysis-cap-binding-proteins-human-cells-exposed-to-physiological

Universidad de Cartagena UDEC

Research

JoVE Journal

Genetics

7.7K Views.  University of Guelph. Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

Video: Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

Measuring mRNA Levels Over Time During the Yeast S. cerevisiae Hypoxic Response

Complex changes in gene expression typically mediate a large portion of a cellular response. Each gene may change expression with unique kinetics as the gene is regulated by the particular timing of one of many stimuli, signaling pathways or secondary effects. In order to capture the entire gene expression response to hypoxia in the yeast S. cerevisiae, RNA-seq analysis was used to monitor the mRNA levels of all genes at specific times after exposure to hypoxia. Hypoxia was established by growing cells in ~100% N2 gas. Importantly, unlike other hypoxic studies, ergosterol and unsaturated fatty acids were not added to the media because these metabolites affect gene expression. Time points were chosen in the range of 0 - 4 h after hypoxia because that period captures the major changes in gene expression. At each time point, mid-log hypoxic cells were quickly filtered and frozen, limiting exposure to O2 and concomitant changes in gene expression. Total RNA was extracted from cells and used to enrich for mRNA, which was then converted to cDNA. From this cDNA, multiplex libraries were created and eight or more samples were sequenced in one lane of a next-generation sequencer. A post-sequencing pipeline is described, which includes quality base trimming, read mapping and determining the number of reads per gene. DESeq2 within the R statistical environment was used to identify genes that change significantly at any one of the hypoxic time points. Analysis of three biological replicates revealed high reproducibility, genes of differing kinetics and a large number of expected O2-regulated genes. These methods can be used to study how the cells of various organisms respond to hypoxia over time and adapted to study gene expression during other cellular responses.

Measuring mRNA Levels Over Time During the Yeast S. cerevisiae Hypoxic Response

Here, we present a protocol using RNA-seq to monitor mRNA levels over time during the hypoxic response of S. cerevisiae cells. This method can be adapted to analyze gene expression during any cellular response.

מדידת רמות ה-mRNA לאורך זמן במהלך שמרים ס' cerevisiae ובשפתיים התגובה

Complex changes in gene expression typically mediate a large portion of a cellular response. Each gene may change expression with unique kinetics as the ...

Tracking Hypoxic Signaling within Encapsulated Cell Aggregates

In Diabetes mellitus type 1, autoimmune destruction of the pancreatic &beta;-cells results in loss of insulin production and potentially lethal hyperglycemia. As an alternative treatment option to exogenous insulin injection, transplantation of functional pancreatic tissue has been explored1,2. This approach offers the promise of a more natural, long-term restoration of normoglycemia. Protection of the donor tissue from the host's immune system is required to prevent rejection and encapsulation is a method used to help achieve this aim.
Biologically-derived materials, such as alginate3 and agarose4, have been the traditional choice for capsule construction but may induce inflammation or fibrotic overgrowth5 which can impede nutrient and oxygen transport. Alternatively, synthetic poly(ethylene glycol) (PEG)-based hydrogels are non-degrading, easily functionalized, available at high purity, have controllable pore size, and are extremely biocompatible,6,7,8. As an additional benefit, PEG hydrogels may be formed rapidly in a simple photo-crosslinking reaction that does not require application of non-physiological temperatures6,7. Such a procedure is described here. In the crosslinking reaction, UV degradation of the photoinitiator, 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), produces free radicals which attack the vinyl carbon-carbon double bonds of dimethacrylated PEG (PEGDM) inducing crosslinking at the chain ends. Crosslinking can be achieved within 10 minutes. PEG hydrogels constructed in such a manner have been shown to favorably support cells7,9, and the low photoinitiator concentration and brief exposure to UV irradiation is not detrimental to viability and function of the encapsulated tissue10. While we methacrylate our PEG with the method described below, PEGDM can also be directly purchased from vendors such as Sigma.
An inherent consequence of encapsulation is isolation of the cells from a vascular network. Supply of nutrients, notably oxygen, is therefore reduced and limited by diffusion. This reduced oxygen availability may especially impact &beta;-cells whose insulin secretory function is highly dependent on oxygen11-13. Capsule composition and geometry will also impact diffusion rates and lengths for oxygen. Therefore, we also describe a technique for identifying hypoxic cells within our PEG capsules. Infection of the cells with a recombinant adenovirus allows for a fluorescent signal to be produced when intracellular hypoxia-inducible factor (HIF) pathways are activated14. As HIFs are the primary regulators of the transcriptional response to hypoxia, they represent an ideal target marker for detection of hypoxic signaling15. This approach allows for easy and rapid detection of hypoxic cells. Briefly, the adenovirus has the sequence for a red fluorescent protein (Ds Red DR from Clontech) under the control of a hypoxia-responsive element (HRE) trimer. Stabilization of HIF-1 by low oxygen conditions will drive transcription of the fluorescent protein (Figure 1). Additional details on the construction of this virus have been published previously15. The virus is stored in 10% glycerol at -80&deg; C as many 150 &mu;L aliquots in 1.5 mL centrifuge tubes at a concentration of 3.4 x 1010 pfu/mL. 
Previous studies in our lab have shown that MIN6 cells encapsulated as aggregates maintain their viability throughout 4 weeks of culture in 20% oxygen. MIN6 aggregates cultured at 2 or 1% oxygen showed both signs of necrotic cells (still about 85-90% viable) by staining with ethidium bromide as well as morphological changes relative to cells in 20% oxygen. The smooth spherical shape of the aggregates displayed at 20% was lost and aggregates appeared more like disorganized groups of cells. While the low oxygen stress does not cause a pronounced drop in viability, it is clearly impacting MIN6 aggregation and function as measured by glucose-stimulated insulin secretion15. Western blot analysis of encapsulated cells in 20% and 1% oxygen also showed a significant increase in HIF-1&alpha; for cells cultured in the low oxygen conditions which correlates with the expression of the DsRed DR protein.

A method for photo-encapsulation of cells in a crosslinked PEG hydrogel is described. Hypoxic signaling within encapsulated murine insulinoma (MIN6) aggregates is tracked using a fluorescent marker system. This system allows serial examination of cells within a hydrogel scaffold and correlation of hypoxic signaling with changes in cell phenotype.

איתות hypoxic מעקב בתוך תא מצרפי Encapsulated

In Diabetes mellitus type 1, autoimmune destruction of the pancreatic &beta;-cells results in loss of insulin production and potentially lethal ...

Bioengineering

Proteomic Analysis of Human Macrophage Polarization Under a Low Oxygen Environment

Macrophages are innate immune cells involved in a number of physiological functions ranging from responses to infectious pathogens to tissue homeostasis. The various functions of these cells are related to their activation states, which is also called polarization. The precise molecular description of these various polarizations is a priority in the field of macrophage biology. It is currently acknowledged that a multidimensional approach is necessary to describe how polarization is controlled by environmental signals. In this report, we describe a protocol designed to obtain the proteomic signature of various polarizations in human macrophages. This protocol is based on a label-free quantification of macrophage protein expression obtained from in-gel fractionated and Lys C/trypsin-digested cellular lysis content. We also provide a protocol based on in-solution digestion and isoelectric focusing fractionation to use as an alternative. Because oxygen concentration is a relevant environmental parameter in tissues, we use this protocol to explore how atmospheric composition or a low oxygen environment affects the classification of macrophage polarization.

We present a protocol to obtain proteomic signatures of human macrophages and apply this to determination of the impact of a low oxygen environment on macrophage polarization.

ניתוח פרוטיאומיה מבנית של קיטוב מקרופאג האנושי תחת סביבה חמצן נמוך

Macrophages are innate immune cells involved in a number of physiological functions ranging from responses to infectious pathogens to tissue homeostasis. ...

Biochemistry

מעקב איזוטופים יציב וניתוח LC-MS למדידת פעילויות DHODH ו-SDH

Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals

The flow of electrons in the mitochondrial electron transport chain (ETC) supports multifaceted biosynthetic, bioenergetic, and signaling functions in mammalian cells. As oxygen (O2) is the most ubiquitous terminal electron acceptor for the mammalian ETC, the O2 consumption rate is frequently used as a proxy for mitochondrial function. However, emerging research demonstrates that this parameter is not always indicative of mitochondrial function, as fumarate can be employed as an alternative electron acceptor to sustain mitochondrial functions in hypoxia. This article compiles a series of protocols that allow researchers to measure mitochondrial function independently of the O2 consumption rate. These assays are particularly useful when studying mitochondrial function in hypoxic environments. Specifically, we describe methods to measure mitochondrial ATP production, de novo pyrimidine biosynthesis, NADH oxidation by complex I, and superoxide production. In combination with classical respirometry experiments, these orthogonal and economical assays will provide researchers with a more comprehensive assessment of mitochondrial function in their system of interest.

מחבר זרקור: בדיקות שאינן תלויות בחמצן למדידת תפקוד המיטוכונדריה ביונקים  

Here, we present a compilation of assays to directly measure mitochondrial function in mammalian cells independently of their ability to consume molecular oxygen.

בדיקות שאינן תלויות בחמצן למדידת תפקוד המיטוכונדריה ביונקים

The flow of electrons in the mitochondrial electron transport chain (ETC) supports multifaceted biosynthetic, bioenergetic, and signaling functions in ...

Respirometric Oxidative Phosphorylation Assessment in Saponin-permeabilized Cardiac Fibers

Investigation of mitochondrial function represents an important parameter of cardiac physiology as mitochondria are involved in energy metabolism, oxidative stress, apoptosis, aging, mitochondrial encephalomyopathies and drug toxicity. Given this, technologies to measure cardiac mitochondrial function are in demand. One technique that employs an integrative approach to measure mitochondrial function is respirometric oxidative phosphorylation (OXPHOS) analysis.
The principle of respirometric OXPHOS assessment is centered around measuring oxygen concentration utilizing a Clark electrode. As the permeabilized fiber bundle consumes oxygen, oxygen concentration in the closed chamber declines. Using selected substrate-inhibitor-uncoupler titration protocols, electrons are provided to specific sites of the electron transport chain, allowing evaluation of mitochondrial function. Prior to respirometric analysis of mitochondrial function, mechanical and chemical preparatory techniques are utilized to permeabilize the sarcolemma of muscle fibers. Chemical permeabilization employs saponin to selectively perforate the cell membrane while maintaining cellular architecture.
This paper thoroughly describes the steps involved in preparing saponin-skinned cardiac fibers for oxygen consumption measurements to evaluate mitochondrial OXPHOS. Additionally, troubleshooting advice as well as specific substrates, inhibitors and uncouplers that may be used to determine mitochondria function at specific sites of the electron transport chain are provided. Importantly, the described protocol may be easily applied to cardiac and skeletal tissue of various animal models and human samples.

Saponin-permeabilized fiber preparation in conjunction with respirometric oxidative phosphorylation analysis provides integrative assessment of mitochondrial function. Mitochondrial respiration in physiological and pathological states can reflect various regulatory influences including mitochondrial interactions, morphology and biochemistry.

הערכה Respirometric זרחון חמצוני ב-Saponin permeabilized סיבים לב

Investigation of mitochondrial function represents an important parameter of cardiac physiology as mitochondria are involved in energy metabolism, ...

Biology

Intra-cardiac Side-Firing Light Catheter for Monitoring Cellular Metabolism using Transmural Absorbance Spectroscopy of Perfused Mammalian Hearts

Absorbance spectroscopy of cardiac muscle provides non-destructive assessment of cytosolic and mitochondrial oxygenation via myoglobin and cytochrome absorbance respectively. In addition, numerous aspects of the mitochondrial metabolic status such as membrane potential and substrate entry can also be estimated. To perform cardiac wall transmission optical spectroscopy, a commercially available side-firing optical fiber catheter is placed in the left ventricle of the isolated perfused heart as a light source. Light passing through the heart wall is collected with an external optical fiber to perform optical spectroscopy of the heart in near real- time. The transmission approach avoids numerous surface scattering interference occurring in widely used reflection approaches. Changes in transmural absorbance spectra were deconvolved using a library of chromophore reference spectra, providing quantitative measures of all the known cardiac chromophores simultaneously. This spectral deconvolution approach eliminated intrinsic errors that may result from using common dual wavelength methods applied to overlapping absorbance spectra, as well as provided a quantitative evaluation of the goodness of fit. A custom program was designed for data acquisition and analysis, which permitted the investigator to monitor the metabolic state of the preparation during the experiment. These relatively simple additions to the standard heart perfusion system provide a unique insight into the metabolic state of the heart wall in addition to conventional measures of contraction, perfusion, and substrate/oxygen extraction.

Here we introduce a method for using an intra-ventricle optical catheter in perfused hearts to perform absorbance spectroscopy across the heart wall. The data obtained provides robust information on tissue oxygen tension as well as substrate utilization and membrane potential simultaneously with cardiac performance measures in this ubiquitous preparation.

מהצד הפנים-לב-אש קטטר אור עבור ניטור מטבוליזם הסלולר באמצעות בליעה בספיגת העבר של הלבבות המגברים

Absorbance spectroscopy of cardiac muscle provides non-destructive assessment of cytosolic and mitochondrial oxygenation via myoglobin and cytochrome ...

Biochemical Titration of Glycogen In vitro

Glycogen is the main energetic polymer of glucose in vertebrate animals and plays a crucial role in whole body metabolism as well as in cellular metabolism. Many methods to detect glycogen already exist but only a few are quantitative. We describe here a method using the Abcam Glycogen assay kit, which is based on specific degradation of glycogen to glucose by glucoamylase. Glucose is then specifically oxidized to a product that reacts with the OxiRed probe to produce fluorescence. Titration is accurate, sensitive and can be achieved on cell extracts or tissue sections. However, in contrast to other techniques, it does not give information about the distribution of glycogen in the cell. As an example of this technique, we describe here the titration of glycogen in two cell lines, Chinese hamster lung fibroblast CCL39 and human colon carcinoma LS174, incubated in normoxia (21% O2) versus hypoxia (1% O2). We hypothesized that hypoxia is a signal that prepares cells to synthesize and store glycogen in order to survive1.

Biochemical Titration of Glycogen In vitro

We describe here an accurate, reproducible and convenient biochemical method for titration of glycogen in vitro. This technique uses the Abcam Glycogen assay kit and is based on successive hydrolysis of glycogen to glucose and glucose titration by fluorescence.

כותרות ביוכימית של גליקוגן<em&gt; במבחנה</em

Glycogen is the main energetic polymer of glucose in vertebrate animals and plays a crucial role in whole body metabolism as well as in cellular ...

Analysis of Global RNA Synthesis at the Single Cell Level following Hypoxia

Hypoxia or lowering of the oxygen availability is involved in many physiological and pathological processes. At the molecular level, cells initiate a particular transcriptional program in order to mount an appropriate and coordinated cellular response. The cell possesses several oxygen sensor enzymes that require molecular oxygen as cofactor for their activity. These range from prolyl-hydroxylases to histone demethylases. The majority of studies analyzing cellular responses to hypoxia are based on cellular populations and average studies, and as such single cell analysis of hypoxic cells are seldom performed. Here we describe a method of analysis of global RNA synthesis at the single cell level in hypoxia by using Click-iT RNA imaging kits in an oxygen controlled workstation, followed by microscopy analysis and quantification.&nbsp; Using cancer cells exposed to hypoxia for different lengths of time, RNA is labeled and measured in each cell. This analysis allows the visualization of temporal and cell-to-cell changes in global RNA synthesis following hypoxic stress.

We describe a technique for analysis of global RNA synthesis in hypoxia using imaging. Click-chemistry labeling of RNA has not previously been performed under hypoxia and allows visualization of global RNA changes at the single cell level. This approach complements the existing averaged RNA techniques, allowing direct visualization of cell-to-cell changes in global RNA synthesis.

ניתוח של גלובל RNA סינתזה ברמת התא בודד הבאות היפוקסיה

Hypoxia or lowering of the oxygen availability is involved in many physiological and pathological processes. At the molecular level, cells initiate a ...

ניתוח של חלבונים קושרי שווי בתאים אנושיים חשופים לתנאי חמצן פיזיולוגיים

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מדידת רמות ה-mRNA לאורך זמן במהלך שמרים ס' cerevisiae ובשפתיים התגובה

איתות hypoxic מעקב בתוך תא מצרפי Encapsulated

ניתוח פרוטיאומיה מבנית של קיטוב מקרופאג האנושי תחת סביבה חמצן נמוך

בדיקות שאינן תלויות בחמצן למדידת תפקוד המיטוכונדריה ביונקים

בדיקות שאינן תלויות בחמצן למדידת תפקוד המיטוכונדריה ביונקים

בדיקות שאינן תלויות בחמצן למדידת תפקוד המיטוכונדריה ביונקים

הערכה Respirometric זרחון חמצוני ב-Saponin permeabilized סיבים לב

מהצד הפנים-לב-אש קטטר אור עבור ניטור מטבוליזם הסלולר באמצעות בליעה בספיגת העבר של הלבבות המגברים

כותרות ביוכימית של גליקוגן

ניתוח של גלובל RNA סינתזה ברמת התא בודד הבאות היפוקסיה