CLONING AND CHARACTERIZATION OF A NOVEL CLASS-II PHOSPHOINOSITIDE 3-KINASE CONTAINING C2 DOMAIN

Phosphoinositide 3-kinases (PI3Ks) have been shown to play critical ro les in cell growth, differentiation, survival, and vesicular transport . Class II PI3Ks have been recently identified in mouse and human (PI3 K-C2 alpha/m-p170/m-cpk and HsC2-PI3K) and in Drosophila (PI3K_68D/cpk ) which contain C2 domain at the C-terminus, However, their physiologi cal function is largely unknown. We report here cloning and characteri zation of murine PI3K-C2 gamma, a novel class II PI3K. The catalytic d omain as well as C2 domain are highly conserved in the Class II PI3K f amily, while the N-terminal regions of these proteins share little sim ilarity. Unlike other Class II PI3Ks, PI3K-C2 gamma exclusively expres sed in the liver, and a N-terminal truncated form was found in lung an d a certain hematopoietic cell line. Specific antiserum against PI3K-C 2 gamma precipitated PI3K activity from the membrane fraction of mouse liver but not from heart. Recombinant PI3K-C2 gamma exhibited a restr icted lipid substrate specificity; it phosphorylated phosphatidylinosi tol (PtdIns) and PtdIns4P but not PtdIns(4,5)P-2. Deletion mutations r evealed that both the N-terminal region and the C2 domain were critica l for enzymatic activity. The murine PI3K-C2 gamma gene locus was mapp ed to the distal region of mouse chromosome 6 in a region of homology with human chromosome 12p, which is distinct from the position of HsC2 -PI3K. Cloning and biochemical characterization of the third member of class II PI3Ks provide a new insight into the function of this subfam ily of PI3Ks. (C) 1998 Academic Press.