Secretion of the mammalian Sec14p-like phosphoinositide-binding p45 protein.
Protein-lipid interactions are important for protein targeting, signal transduction, lipid transport, and the maintenance of cellular compartments and membranes. Specific lipid-binding protein domains, such as PH, FYVE, PX, PHD, C2 and SEC14 homology domains, mediate interactions between proteins and specific phospholipids. We recently cloned a 45-kDa protein from rat olfactory epithelium, which is homologous to the yeast Sec14p phosphatidylinositol (PtdIns) transfer protein and we report here that this protein binds to PtdIns(3,4,5)P3 and far weaker to less phosphorylated derivatives of PtdIns. Expression of the p45 protein in COS-1 cells resulted in accumulation of the protein in secretory vesicles and in the extracellular space. The secreted material contained PtdIns(3,4,5)P3. Our findings are the first report of a Sec14p-like protein involved in transport out of a cell and, to the best of our knowledge, inositol-containing phospholipids have not previously been detected in the extracellular space. Our findings suggest that p45 and phosphoinositides may participate in the formation of the protective mucus on nasal epithelium.
Merkulova
Maria
M
Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Huynh
Huong
H
Radchenko
Vitaly
V
Saito
Kan
K
Lipkin
Valery
V
Shuvaeva
Tatiana
T
Mustelin
Tomas
T
D000818:Animals; D043423:Carboxypeptidase H / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D008970:Molecular Weight; D010716:Phosphatidylinositols / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins / Q000737:chemistry*; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*
D002352:Carrier Proteins; D010716:Phosphatidylinositols; D049294:Phospholipid Transfer Proteins; C483438:SEC14 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C506000:Sec14p-like phosphoinositide-binding p45 protein, rat; D043423:Carboxypeptidase H