Endurance part 3+4 Flashcards
(13 cards)
What is CRISPR-cas?
Genetic scissors that can snip part of a gene out and stick other parts in
How does transgenesis of cells in mice work?
We need to access the nucleus (via viruses), fuse with cell and implant proteins that edit genes.
What does FCCP do?
Takes the breaks off respiration by allowing protons to flood into the mitochondrial matrix, heres how:
1) Mitochondria normally generate ATP using a proton gradient across the inner membrane.
2) FCCP collapses this gradient by transporting protons (H⁺) across the membrane.
3) As a result, the electron transport chain (ETC) keeps running, but ATP is not produced efficiently.
4) This leads to increased oxygen consumption without ATP generation.
According to Spiegelman et al 1999, what does PGC1-a overexpression cause?
Increased mitochondrial respiration and biogenesis (content) in cells.
- Basal, FCCP, and oligomycin all increase with more PGC1-a, leading to more mitochondria and more respiration.
What are the 3 processes of PGC1-a activation in skeletal muscle?
- Increase PGC1-a transcription (initiator)
- Increase PGC1-a nuclear abundance (increased function/activity)
- Increased post-translational modification of PGC1-a (increasing it’s stability and function)
With regards to PGC1-a transcription, what does Akimoto et al 2004 show us?
Deletion of MEF2 and CRE (these are required for PGC1-a transcription) blocks induction of PGC1-a
These elements are bindings sites for specific transcription factors. When cells receive signals from exercise, transcription factors bind to MEF2 and CRE to activate PGC1-a gene transcription. If MEF2 and CRE are deleted, transcription factors cannot bind so PGC1-a gene can’t be switched on.
What findings does Wright et al 2007 show us about exercise induced PGC1-a expression
Exercise induced mitochondrial biogenesis begins before an increase in muscle PGC1-a expression.
Exercise results in increased PGC1-a nuclear protein content, suggesting PGC1-a translocation (from cytosol) to the nucleus is a pivotal 1st step in initiating mitochondrial biogenesis
In simple terms: Exercise doesn’t wait for new PGC-1α to be made. It first uses what’s already there, moving it into the nucleus to kick off the process of building more mitochondria.
What is a key process in increased post-translational modification?
Phosphorylation - very important as it can drastically change protein function
How does skeletal muscle use phosphorylation to adapt?
AMPK - activated by low energy (increased AMP). AMPK phosphorylates targets to: promote glucose uptake + FA oxidation, also stimulate PGC1-a (leading to mitochondrial biogenesis).
AMPK is a heterotrimer (alpha, beta gamma) each of which regulates an aspect of its function
Garcia-Roves et al 2008 - skeletal muscle mitochondrial biogenesis is increased in TG-AMPK y3 225Q mice. What is this?
Tg-AMPKγ3^225Q refers to a transgenic mouse model engineered to express a mutant form of the AMPK γ3 subunit—specifically, the R225Q mutation—predominantly in skeletal muscle.
This mutation is characterized as a gain-of-function, meaning it enhances the activity of the AMPK complex, meaning more mitochondrial biogenesis.
O’neill et al 2011 demonstrated the importance of AMPK for exercise tolerance, how?
Muscle specific decrease in AMPK phosphorylation and subunit expression in AMPK B1 and B2 mice (both AMPK subunits knocked out) = a dramatic decrease in exercise tolerance (significant decrease in distance and speed)
What does AICAR do? *detail not needed in exam
1) AICAR enters cells and is converted to ZMP, a molecule that mimics AMP.
2) ZMP binds to the γ subunit of AMPK, just like AMP does.
3) This activates AMPK, even without a drop in cellular energy (ATP).
4) Once AMPK is activated, it triggers a cascade of effects aimed at:
- Restoring energy balance
- Increasing catabolic (ATP-generating) processes
- Decreasing anabolic (ATP-consuming) processes
Jager et al 2007 has a seminal study on AICAR, what does this study show?
Activating AMPK via AICAR enhances PGC-1a promoter, but mutating AMPK phosphorylation sites on PGC1-a removes this effect.
This shows AMPK directly phosphorylates and activates PGC1-a gene expression.
