Phosphoinositide 3-kinase gamma is preferentially expressed in leukocytes.
PI3K gamma is activated by beta gamma subunits of heterotrimeric G-proteins
, which thus link seven transmembrane helix receptor activation to phosphat
idylinositol ( 3,4,5)-trisphosphate production. Here we describe the molecu
lar cloning of the murine PI3K gamma cDNA, the PI3K gamma gene structure, i
ts chromosomal assignment and the analysis of promoter activity. The mouse
cDNA shares 86% identity to its pig and human orthologues at the nucleotide
level. The MmPI3K gamma gene spans approximately 30 kb and comprises 11 ex
ons. RACE-PCR indicated the presence of multiple start sites generating 5'
UTRs with different lengths, the longest being 874 bp. The putative promote
r region contains no TATA box but several putative binding sites for hemato
poietic specific transcription factors. A 1200 bp long sequence upstream th
e first transcription start site was found to possess tissue specific promo
ter activity. Deletion constructs revealed two contiguous regions, with act
ivator function, ranging from positions -139 to -557, and with inhibitory f
unction, ranging from positions -557 to -892. FISH analysis revealed that t
he MmPI3K gamma is located on chromosome 12 band B and that the human ortho
logue is positioned on chromosome 7q22.2-22.3. In spite of some differences
in the ATP-binding site, recombinant murine PI3K gamma protein is equally
sensitive to wortmannin as its human counterpart. This suggests that mouse
models will provide reliable results in the assessments of novel PI3K gamma
inhibitors. (C) 2000 Elsevier Science B.V. All rights reserved.