Cloning and characterization of a novel class II phosphoinositide 3-kinase containing C2 domain.
Phosphoinositide 3-kinases (PI3Ks) have been shown to play critical roles in cell growth, differentiation, survival, and vesicular transport. Class II PI3Ks have been recently identified in mouse and human (PI3K-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 physiological function is largely unknown. We report here cloning and characterization of murine PI3K-C2 gamma, a novel class II PI3K. The catalytic domain as well as C2 domain are highly conserved in the Class II PI3K family, while the N-terminal regions of these proteins share little similarity. Unlike other Class II PI3Ks, PI3K-C2 gamma exclusively expressed in the liver, and a N-terminal truncated form was found in lung and a certain hematopoietic cell line. Specific antiserum against PI3K-C2 gamma precipitated PI3K activity from the membrane fraction of mouse liver but not from heart. Recombinant PI3K-C2 gamma exhibited a restricted lipid substrate specificity; it phosphorylated phosphatidylinositol (PtdIns) and PtdIns4P but not PtdIns(4,5)P2. Deletion mutations revealed that both the N-terminal region and the C2 domain were critical for enzymatic activity. The murine PI3K-C2 gamma gene locus was mapped 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 subfamily of PI3Ks.
Misawa
H
H
Institute of Life Science, Kurume University, Japan.
Ohtsubo
M
M
Copeland
N G
NG
Gilbert
D J
DJ
Jenkins
N A
NA
Yoshimura
A
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D018129:Phosphatidylinositol Phosphates; D017384:Sequence Deletion; D013379:Substrate Specificity; D014018:Tissue Distribution
D018076:DNA, Complementary; D018129:Phosphatidylinositol Phosphates; D019869:Phosphatidylinositol 3-Kinases