| First Author | Martinez LO | Year | 2003 |
| Journal | J Biol Chem | Volume | 278 |
| Issue | 39 | Pages | 37368-74 |
| PubMed ID | 12869555 | Mgi Jnum | J:85674 |
| Mgi Id | MGI:2675932 | Doi | 10.1074/jbc.M307161200 |
| Citation | Martinez LO, et al. (2003) Phosphorylation of a pest sequence in ABCA1 promotes calpain degradation and is reversed by ApoA-I. J Biol Chem 278(39):37368-74 |
| abstractText | ATP-binding cassette transporter A1 (ABCA1), the defective molecule in Tangier disease, mediates the apoAI-dependent efflux of excess cholesterol from cells. We recently showed that ABCA1 proteolysis by calpain was dependent on a PEST sequence in the cytoplasmic region of ABCA1 and was reversed by apoA-I interaction with ABCA1. We show here that phosphorylation of ABCA1 in HEK293 cells was reduced by 63 +/- 2.4% after removal of the PEST sequence (ABCA1delPEST) or by incubation of cells with apoAI (58 +/- 3.3%). By contrast, ABCA1delPEST showed no further decrease of phosphorylation upon apoAI treatment. To assess the hypothesis that PEST sequence phosphorylation could regulate ABCA1 calpain proteolysis, we mutagenized S/T residues in the PEST sequence and identified Thr-1286 and Thr-1305 as constitutively phosphorylated residues. The ABCA1-T1286A/T1305A mutant was not degraded by calpain and was not further stabilized upon apoA-I treatment. The T1286A/T1305A mutant showed a 3.1-fold increase in cell surface expression and a 2.3-fold increase of apoAI-mediated cholesterol efflux compared with wild type ABCA1. In conclusion, we propose a mechanism of regulation of ABCA1 cell surface expression and function in which the interaction with apoA-I results in dephosphorylation of the ABCA1 PEST sequence and thereby inhibits calpain degradation leading to an increase of ABCA1 cell surface expression. |
