Multisite phosphorylation of oxysterol-binding protein regulates sterol binding and activation of sphingomyelin synthesis

• DOI: 10.1091/mbc.e12-04-0283
• Publication Date: 2012-08-09T06:07:58Z
• Authors: Asako Goto; Xinwei Liu; Carolyn-Ann Robinson; Neale D. Ridgway
• Keywords: Oxysterol

The endoplasmic reticulum (ER)-Golgi sterol transfer activity of oxysterol-binding protein (OSBP) regulates sphingomyelin (SM) synthesis, as well post-Golgi cholesterol efflux pathways. phosphorylation and ER-Golgi localization OSBP are correlated, suggesting this modification the directionality and/or specificity activity. In paper, we report that on two serine-rich motifs, S381-S391 (site 1) S192, S195, S200 2), specifically controls at ER. A phosphomimetic SM/cholesterol-sensitive site 1 (OSBP-S5E) had increased in vitro 25-hydroxycholesterol-binding capacity, extraction from liposomes, but reduced Phosphatidylinositol 4-phosphate (PI(4)P) competed for a common binding OSBP; however, direct PI(4)P was not affected by phosphorylation. Individual 2 phosphomutants supported oxysterol activation SM synthesis OSBP-deficient CHO cells. However, double site1/2 mutant (OSBP-S381A/S3D) deficient constitutively colocalized with vesicle-associated membrane protein-associated (VAP-A) collapsed ER network. This study identifies regulation VAP-A ER, an alternate ligand could be exchanged Golgi apparatus.