Phosphorylation of StarD10 on serine 284 by casein kinase II modulates its lipid transfer activity.
StarD10 is a dual specificity lipid transfer protein capable of shuttling phosphatidylcholine and phosphatidylethanolamine between membranes in vitro. We now provide evidence that, in vivo, StarD10 is phosphorylated on serine 284. This novel phosphorylation site was identified by tandem mass spectrometry of immunoaffinity-purified StarD10 from lysates of HEK293T cells transiently expressing the protein. In vitro kinase assays revealed that casein kinase II was capable of phosphorylating wild-type StarD10 but not a S284A mutant protein. Interestingly, hypotonic extracts prepared from HEK293T cells expressing the serine to alanine mutant exhibited increased lipid transfer activity compared with those from wild-type StarD10-expressing cells, suggesting that, in a cellular context, phosphorylation on serine 284 negatively regulates StarD10 activity. Because casein kinase II phosphorylation also inhibited lipid transfer activity of the purified recombinant StarD10 protein, inhibition is not dependent on any cellular cofactors. Instead, our data show that C-terminal StarD10 phosphorylation on serine 284 regulates its association with cellular membranes.
Olayioye
Monilola A
MA
Institute of Cell Biology and Immunology, University of Stuttgart, Allmandring 31, Stuttgart 70569, Germany. monilola.olayioye@izi.uni-stuttgart.de
Buchholz
Michael
M
Schmid
Simone
S
Schöffler
Patrik
P
Hoffmann
Peter
P
Pomorski
Thomas
T
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism; D002460:Cell Line; D015180:Electrophoresis, Gel, Two-Dimensional; D005786:Gene Expression Regulation; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry*; D013552:Swine
D008055:Lipids; D010750:Phosphoproteins; C488090:STARD10 protein, human; D012694:Serine; D047390:Casein Kinase II