title: Regulation of autophagosome formation by Rho kinase.
abstract: Macroautophagy, commonly referred to as autophagy, is a protein degradation pathway that functions at a constitutive level in cells, which may become further activated by stressors such as nutrient starvation or protein aggregation. Autophagy has multiple beneficial roles for maintaining normal cellular homeostasis and these roles are related to the implications of autophagy in disease mechanisms including neurodegeneration and cancer. We previously searched for novel autophagy regulators and identified Rho-kinase 1 (ROCK1) as a candidate. Here, we show that activated ROCK1 inhibits autophagy in human embryonic kidney 293 cells. Conversely, ROCK inhibitory compounds enhanced the autophagy response to amino acid starvation or rapamycin treatment. Inhibition of ROCK during the starvation period led to a more rapid response with the production of larger early autophagosomes that matured into enlarged late degradative autolysosomes. Despite the production of enlarged LC3-positive early autophagosomes, membrane precursors containing WD-repeat protein interacting with phosphoinositides 1 (WIPI1) and mammalian Atg9 were not affected by ROCK inhibition, suggesting that phagophore elongation had been unusually extended. However, the enlarged autophagosomes were enriched in ULK1 which was essential to allow progression of autophagy flux. Our results demonstrate a novel role for ROCK in the control of autophagosome size and degradative capacity.
authors.affiliation: Beatson Institute for Cancer Research, Glasgow, G61 1BD, UK.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Mleczak
authors.forename: Sarah
authors.initials: S
authors.lastname: Millar
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Tooze
authors.forename: Michael F
authors.initials: MF
authors.lastname: Olson
authors.forename: Edmond Y W
authors.initials: EY
authors.lastname: Chan
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects*; D000071189:Autophagy-Related Protein-1 Homolog; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology*; D033921:Vesicular Transport Proteins; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D000903:Antibiotics, Antineoplastic; C574794:ATG9A protein, human; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C477012:MAP1LC3A protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D047428:Protein Kinase Inhibitors; D033921:Vesicular Transport Proteins; C522812:WIPI1 protein, human; D000071189:Autophagy-Related Protein-1 Homolog; D017346:Protein Serine-Threonine Kinases; C515851:ROCK1 protein, human; C484754:ULK1 protein, human; D054460:rho-Associated Kinases; D020123:Sirolimus