Posted on May 3, 2021
The ceramide transport protein CERT mediates the inter-organelle transport of ceramide for the synthesis of sphingomyelin, presumably through endoplasmic reticulum (ER)-Golgi membrane contact sites
The ceramide transport protein CERT mediates the inter-organelle transport of ceramide for the synthesis of sphingomyelin, presumably through endoplasmic reticulum (ER)-Golgi membrane contact sites. S315E induced intracellular punctate structures, to which CERT and VAP were co-localized, and the occurrence of the structure was dependent on both phosphatidylinositol 4-monophosphate binding and VAP binding activities of CERT. Phosphorylation of another region (named a serine-rich motif) in CERT is known to down-regulate the activity of CERT. Analysis of various CERT mutant constructs showed that the de-phosphorylation of the serine-rich motif and the phosphorylation of Ser-315 likely have the additive contribution to enhance the activity of CERT. These results demonstrate that the phosphorylation of CERT at the FFAT motif-adjacent serine affected its affinity for VAP, which may regulate the inter-organelle trafficking of ceramide in response to the perturbation of cellular sphingomyelin and/or other sphingolipids. schematic view of the structure of human CERT and the amino acid sequence containing Ser-315 near the FFAT motif (GenBankTM accession number “type”:”entrez-protein”,”attrs”:”text”:”NP_112729″,”term_id”:”14165452″,”term_text”:”NP_112729″NP_112729). The core region of the FFAT motif is highlighted by a represents the position of Ser-315. HeLa-S3 cells were transfected with an expression plasmid encoding HA-CERT WT, HA-CERT S315A, or a clear vector and cultured for 48 h before harvesting. Cell lysates had been ready with previously referred to lysis buffer (29) and put through SDS-PAGE accompanied by Traditional western blotting (amino acidity sequences (312C331) across the FFAT theme of various human being CERT constructs are demonstrated. The core area from the FFAT theme AB05831 is highlighted with AB05831 a represents the positioning of Ser-315, as well as the mutated residues are in digitonin components had been ready from CHO-K1 cells co-expressing the indicated HA-CERT constructs and FLAG-VAP-A (Triton X-100 components had been ready from HeLa-S3 cells co-expressing the indicated HA-CERT constructs and FLAG-VAP-A. FLAG-VAP-A was immunoprecipitated through the components and examined by Traditional western blotting using the indicated antibodies. EXPERIMENTAL Methods Materials Dulbecco’s revised AB05831 Eagle’s moderate (DMEM) and Ham’s F-12 moderate had been bought from Wako Pure Chemical substance Sectors (Osaka, Japan). Lipofectamine?, PLUSTM reagent, LipofectamineTM RNAiMAX, and NuPAGE? lithium dodecyl sulfate test buffer (4) had been from Invitrogen. An assortment of protease inhibitors (Complete Protease Inhibitor Blend Tablets) was from Roche Applied Technology. Phosphatase inhibitor blend 2 and phosphatase inhibitor blend 3 had been from Sigma. 1,2-Dioleoyl-lectin (RCA 120) was from Vector Laboratories Inc. sphingomyelinase was from Higeta Shoyu (Tokyo, Japan). Little interfering RNA was from Hokkaido Program Technology (Sapporo, Japan). The next antibodies had been bought: rat monoclonal anti-HA and AB05831 rat monoclonal anti-HA horseradish peroxidase (HRP)-conjugated (Roche Applied Technology); Rabbit polyclonal to AASS rabbit polyclonal anti-protein-disulfide isomerase, mouse monoclonal anti-FLAG HRP-conjugated, anti-FLAG antibody-coupled agarose, and anti-HA antibody-coupled agarose (Sigma); mouse monoclonal anti-GS28 (StressGen); mouse monoclonal anti-GM130 and anti-EEA1 (BD Biosciences); rabbit polyclonal anti-Sec61 (Merck); rabbit monoclonal anti-LAMP1 and anti-syntaxin-6 (Cell Signaling); and supplementary antibodies conjugated to Alexa Fluor 488 and Alexa Fluor 594 (Invitrogen). Antibodies A polyclonal antibody against Ser(P)-315 of human being CERT was produced from the immunization of rabbits using the artificial phosphopeptide CEEGPN(pS)LINEE (residues 310C320 and also a cysteine) conjugated to keyhole limpet hemocyanin using the manufacturer’s regular process (Scrum Inc., Tokyo, Japan). An integral part of the antiserum was affinity-purified by binding to CNBr-activated SepharoseTM 4B (GE health care) conjugated using the phosphopeptide (CEEGPN(pS)LINEE) and moving through that having a nonphosphopeptide (CEEGPNSLINEE). A poultry polyclonal antibody against human being VAP-A was produced from the immunization of hens using the purified recombinant proteins of VAP-A (3C269) using the producers’ regular process (Scrum Inc., Tokyo, Japan). An integral part of the antiserum was affinity-purified by binding to CNBr-activated SepharoseTM 4B (GE Health care) conjugated with purified VAP-A (3-269). Building of HA-tagged CERT Mutants Ser-315-related CERT mutants tagged using the HA epitope had been built by PCR using the pBluescript? II SK(+) (Agilent Systems)-centered plasmid pBS/nHA-hCERT WT (14) (nHA shows HA-tagged in the N terminus, and hCERT shows human CERT), like a template and sets of primers as follows: nHA-hCERT S315A, 5-GAAGGCCCTAACGCTCTGATTAATGAAGAA-3 and 5-TTCATTAATCAGAGCGTTAGGGCCTTCTTC-3; nHA-hCERT S315D, 5-GAAGGCCCTAACGATCTGATTAATGAAGAA-3 and 5-TTCATTAATCAGATCGTTAGGGCCTTCTTC-3; nHA-hCERT S315E, 5-GAAGGCCCTAACGAACTGATTAATGAAGAA-3 and 5-TTCATTAATCAGTTCGTTAGGGCCTTCTTC-3. cDNA fragments containing the mutated site were subcloned into the MluI/XhoI site of pBS/nHA-hCERT WT to make pBS/nHA-hCERT S315A, pBS/nHA-hCERT S315D, and pBS/nHA-hCERT S315E, respectively. cDNA fragments encoding mutated nHA-hCERT were then subcloned from the pBluescript vector into the EcoRI/XhoI sites of pcDNA3.1(+)Neo (Invitrogen) to make pcDNAneo/nHA-hCERT S315A, pcDNAneo/nHA-hCERT S315D, and pcDNAneo/nHA-hCERT S315E, respectively. cDNA fragments encoding the mutated nHA-hCERT were also subcloned into the EcoRI/XhoI site.