Ceramide 1‐phosphate transfer protein depletion in the cell drives autophagic response: potential implications of this newly identified protein in cell death and survival (737.6)

Abstract

Ceramide 1‐Phosphate (C1P) is a biologically active sphingolipid that stimulates cell proliferation, macrophage migration, and inflammatory events. We recently characterized a novel human lipid transfer protein encoded by GLTPD1 on chromosome 1 (locus 1p36.33). We named the protein, ceramide 1‐phosphate transfer protein (CPTP) due to its lipid specificity and discovered that CPTP transports C1P to the plasma membrane from TGN after synthesis by ceramide kinase. CPTP depletion by RNAi leads to C1P accumulation in TGN (~6‐fold), stimulating cPLA2α and inducing pro‐inflammatory eicosanoid production (Simanshu et al., Nature 500: 463‐67, 2013). Here, we investigated whether CPTP depletion leads to programmed cell death and discovered an autophagic response in human cervical cancer cell lines (HeLa) and human lung adenocarcinoma epithelial cells (A549). Transfection with ShRNA (pSuper.GFP.ShRNA.CPTP vector) resulted in GFP‐LC3 puncta and acidophilic acridine orange staining by epifluorescence microscopy and beclin 1(BECN1) overexpression by RT‐PCR. CPTP mutants deficient in C1P binding/transfer (K60A & R106L) also exhibited autophagy. We conclude that normal levels of viable CPTP are needed for cells to suppress autophagy.Grant Funding Source: [Support: NIGMS‐45928 & 72754; Hormel Fnd]