Phospholipase C-related catalytically inactive protein, a novel microtubule-associated protein 1 light chain 3-binding protein, negatively regulates autophagosome formation

• Published in: Biochemical and biophysical research communications 2013-03, Vol.432 (2), p.268-274
• Main Authors: Umebayashi, Hisanori, Mizokami, Akiko, Matsuda, Miho, Harada, Kae, Takeuchi, Hiroshi, Tanida, Isei, Hirata, Masato, Kanematsu, Takashi
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Amino Acid Sequence; Animals; Apoptosis Regulatory Proteins; Autophagy; Catalysis; Cells, Cultured; Cytoskeletal Proteins - metabolism; Fibroblasts - metabolism; GABARAP; LC3; MEF; Membrane Proteins - metabolism; Mice; Mice, Knockout; Microtubule-Associated Proteins - metabolism; Molecular Sequence Data; Phagosomes; PRIP; Type C Phospholipases - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2013.01.119

► PRIP is a novel negative modulator in nutrient depletion-induced autophagy. ► PRIP, a binding partner of GABARAP, interacts with an autophagy initiator, LC3. ► Enhanced PRIP colocalization with LC3 occurs in starved MEFs. ► PRIP deficiency increases autophagosome formation in starved MEFs. ► PRIP overexpression inhibits autophagosome formation in starved MEFs. Upon starvation, cells undergo autophagy, an intracellular bulk-degradation process, to provide the required nutrients. Here, we observed that phospholipase C-related catalytically inactive protein (PRIP) binds to microtubule-associated protein 1 light chain 3 (LC3), a mammalian autophagy-related initiator that regulates the autophagy pathway. Then, we examined the involvement of PRIP in the nutrient depletion-induced autophagy pathway. Enhanced colocalization of PRIP with LC3 was clearly seen in nutrient-starved mouse embryonic fibroblasts under a fluorescent microscope, and interaction of the proteins was revealed by immunoprecipitation experiments with an anti-LC3 antibody. Under starvation conditions, there were more green fluorescent protein fused-LC3 dots in mouse embryonic fibroblasts from PRIP-deficient mice than in fibroblasts from wild type cells. The formation of new dots in a single cell increased, as assessed by time-lapse microscopy. Furthermore, the increase in autophagosome formation in PRIP-deficient cells was notably inhibited by exogenously overexpressed PRIP. Taken together, PRIP is a novel LC3-binding protein that acts as a negative modulator of autophagosome formation.