Molecular cloning and functional characterization of a human homologue of centaurin-alpha.

We report here the molecular cloning, expression, and characterisation of a human homologue of rat centaurin-alpha, which we have termed centaurin-alpha(1). The cDNA contains a single open reading frame, which encodes a 373-amino-acid protein with a calculated molecular weight of 43,429 Daltons. Centaurin-alpha(1) shows high identity at the amino acid level with the other centaurin-alpha homologues, p42(IP4) and PIP(3)BP. Northern analysis revealed that centaurin-alpha(1) expresses as a single 2.5-kb transcript, mainly in the brain. Recombinant centaurin-alpha(1) binds the inositol head group of PtdIns(3,4,5)P(3) and Ins(1,3,4, 5)P(4), with high affinity (K(d) 139.7 +/- 10.5 nM) and inositol phosphate specificity, consistent with it functioning as a putative PtdIns(3,4,5)P(3) receptor. In keeping with this conclusion, we have shown that GFP-tagged centaurin-alpha(1) recruits to the plasma membrane in a PI 3-kinase-dependent manner and the recruitment is inhibited by the PI 3-kinase inhibitor wortmannin. These results suggest that centaurin-alpha(1) can function as an in vivo PtdIns(3, 4,5)P(3) receptor.