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Regulation of JMY's actin nucleation activity by TTC5/STRAP and LC3 during autophagy
1a Life Sciences Institute , University of Michigan , Ann Arbor , MI , USA.
Abstract:
Actin plays indispensable roles in autophagosome biogenesis. Branched actin networks assembled within phagophore membranes are required for generating the autophagosome membrane shape and movement. The ARP2/3 complex and its regulators, such as JMY (junction mediating and regulatory protein, p53 cofactor), translocate to phagophore membranes to promote local actin filament formation during autophagy. Hu et al., recently showed that during autophagy LC3 recruits JMY to the phagophore and promotes its actin nucleation activity. They also characterized TTC5/STRAP (tetratricopeptide repeat domain 5) as a negative autophagy regulator via binding to JMY and antagonizing its activation. Moreover, an in vitro reconstitution system was developed to demonstrate that membrane-bound LC3 is sufficient to recruit JMY and stimulate JMY-mediated actin filament assembly.
Insights
Autophagy utilizes actin networks for autophagosome formation. LC3 recruits JMY to phagophores, promoting actin nucleation, while TTC5/STRAP inhibits this process.
Area of Science:
- Cell Biology
- Molecular Biology
- Autophagy Research
Background:
- Actin dynamics are crucial for autophagosome biogenesis, influencing membrane shape and movement.
- The ARP2/3 complex and its regulators, like JMY, are recruited to phagophore membranes to initiate actin filament assembly.
- LC3 (microtubule-associated protein 1A/1B-light chain 3) is a key protein in autophagosome formation.
Discussion:
- LC3 directly recruits JMY to the phagophore membrane, enhancing its actin nucleation activity during autophagy.
- TTC5/STRAP acts as a negative regulator of autophagy by binding to JMY and inhibiting its activation.
- This study elucidates a novel regulatory mechanism involving LC3, JMY, and TTC5/STRAP in controlling actin dynamics during autophagosome formation.
Key Insights:
- LC3-mediated recruitment of JMY to phagophores is essential for initiating actin nucleation.
- TTC5/STRAP antagonizes JMY activity, providing a negative feedback loop for autophagy regulation.
- An in vitro system confirms that membrane-bound LC3 is sufficient for JMY recruitment and actin assembly.
Outlook:
- Further investigation into the precise structural interactions between LC3, JMY, and TTC5/STRAP.
- Exploring the therapeutic potential of modulating this actin-based pathway in diseases associated with autophagy dysfunction.
- Investigating the role of JMY-mediated branched actin networks in other cellular processes beyond autophagy.