KCS1 deletion in Saccharomyces cerevisiae leads to a defect in translocation of autophagic proteins and reduces autophagosome formation.
Inositol phosphates are implicated in the regulation of autophagy; however, the exact role of each inositol phosphate species is unclear. In this study, we systematically analyzed the highly conserved inositol polyphosphate synthesis pathway in S. cerevisiae for its role in regulating autophagy. Using yeast mutants that harbored a deletion in each of the genes within the inositol polyphosphate synthesis pathway, we found that deletion of KCS1, and to a lesser degree IPK2, led to a defect in autophagy. KCS1 encodes an inositol hexakisphosphate/heptakisposphate kinase that synthesizes 5-IP(7) and IP(8); and IPK2 encodes an inositol polyphosphate multikinase required for synthesis of IP(4) and IP(5). We characterized the kcs1Δ mutant strain in detail. The kcs1Δ yeast exhibited reduced autophagic flux, which might be caused by both the reduction in autophagosome number and autophagosome size as observed under nitrogen starvation. The autophagy defect in kcs1Δ strain was associated with mislocalization of the phagophore assembly site (PAS) and a defect in Atg18 release from the vacuole membrane under nitrogen deprivation conditions. Interestingly, formation of autophagosome-like vesicles was commonly observed to originate from the plasma membrane in the kcs1Δ strain. Our results indicate that lack of KCS1 interferes with proper localization of the PAS, leads to reduction of autophagosome formation, and causes the formation of autophagosome-like structure in abnormal subcellular locations.
Department of Pharmacology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, NJ, USA.
Robert
R
Taylor
Po-Hao
PH
Chen
Chia-Ching
CC
Chou
Jasmin
J
Patel
Shengkan V
SV
Jin
D001343:Autophagy / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D009584:Nitrogen / Q000172:deficiency / Q000494:pharmacology; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000235:genetics* / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
D007295:Inositol Phosphates; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; C425775:ARG82 protein, S cerevisiae; D017853:Phosphotransferases (Alcohol Group Acceptor); D017856:Phosphotransferases (Phosphate Group Acceptor); C098863:KCS1 protein, S cerevisiae; D009584:Nitrogen