The PKA-CREB signaling pathway is involved in many cellular processes including autophagy. Recent studies demonstrated that PKA-CREB inhibits autophagy in yeast; however, the role of PKA-CREB signaling in mammalian cell autophagy has not been fully characterized. Here, we report that the integral membrane protein ITM2A expression is positively regulated by PKA-CREB signaling and ITM2A expression interferes with autophagic flux by interacting with vacuolar ATPase (v-ATPase). The ITM2A promoter contains a CRE element, and mutation at the CRE consensus site decreases the promoter activity. Forskolin treatment and PKA expression activate the ITM2A promoter confirming that ITM2A expression is dependent on the PKA-CREB pathway. ITM2A expression results in the accumulation of autophagosomes and interferes with autolysosome formation by blocking autophagic flux. We demonstrated that ITM2A physically interacts with v-ATPase and inhibits lysosomal function. These results support the notion that PKA-CREB signaling pathway regulates ITM2A expression, which negatively regulates autophagic flux by interfering with the function of v-ATPase.
Keywords: BafA1, bafilomycin A1; CRE, cAMP response element; CREB; CREB, cAMP responsive element binding protein; ChIP, chromatin immunoprecipitation; EBSS, Earle's balanced salt solution; ITM2A; ITM2A, integral membrane protein 2A; LAMP1, lysosomal-associated membrane protein 1; MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 β; MAPK, mitogen-activated protein kinase; MTOR, mechanistic target of rapamycin; PKA; PKA, protein kinase A; SQSTM1, sequestosome 1; TPA, 12-O-tetradecanoylphorbol-13-acetate; autophagy; cAMP, cyclic adenosine monophosphate; tfLC3, tandem fluorescent-tagged LC3; v-ATPase; v-ATPase, vacuolar ATPase..