Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Autophagy, the process for recycling cytoplasm in the lysosome, depends on membrane trafficking. We previously identified Drosophila Sbf as a Rab21 guanine nucleotide exchange factor (GEF) that acts with Rab21 in endosomal trafficking. Here, we show that Sbf/MTMR13 and Rab21 have conserved functions required for starvation-induced autophagy. Depletion of Sbf/MTMR13 or Rab21 blocked endolysosomal trafficking of VAMP8, a SNARE required for autophagosome-lysosome fusion. We show that starvation induces Sbf/MTMR13 GEF and RAB21 activity, as well as their induced binding to VAMP8 (or closest Drosophila homolog, Vamp7). MTMR13 is required for RAB21 activation, VAMP8 interaction and VAMP8 endolysosomal trafficking, defining a novel GEF-Rab-effector pathway. These results identify starvation-responsive endosomal regulators and trafficking that tunes membrane demands with changing autophagy status.
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PMID:Starvation-induced MTMR13 and RAB21 activity regulates VAMP8 to promote autophagosome-lysosome fusion. 2564 48

Autophagy has both tumor-promoting and -suppressing effects in cancer, including colorectal cancer (CRC), with transformed cells often exhibiting high autophagic flux. In established tumors, autophagy inhibition can lead to opposite responses resulting in either tumor cell death or hyperproliferation. The functional mechanisms underlying these differences are poorly understood. The present study aimed to investigate the relationship between the autophagic capacities of CRC cells and their sensitivities to autophagy inhibition. All studied CRC cell lines showed high basal autophagic flux. However, only HCT116 and Caco-2/15 cells displayed regulated autophagic flux upon starvation. Knockdown of ATG5 (which disrupts autophagosome elongation) or RAB21 (which decreases autophagosome/lysosome fusion) had little effect on CRC cell proliferation in vitro. Nonetheless, inhibition of autophagy in vivo had a substantial cell line-dependent impact on tumor growth, with some cells displaying decreased (HCT116 and Caco-2/15) or increased (SW480 and LoVo) proliferation. RNA sequencing and Western blot analyses in hyperproliferative SW480 tumors revealed that the mTORC2 and AKT pathways were hyperactivated following autophagy impairment. Inhibition of either mTOR or AKT activities rescued the observed hyperproliferation in autophagy-inhibited SW480 and reduced tumor growth. These results highlight that autophagy inhibition can lead, in specific cellular contexts, to compensatory mechanisms promoting tumor growth.
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PMID:Colorectal cancer cells respond differentially to autophagy inhibition in vivo. 3138 75