Phosphoinositide 3-kinase (PI3K)는 항산화 제어반응, 심근세포 성장, 및 세포 내 특수반응 뿐만 아니라 세포분화, 생장, 운동, 식균 및 내항작용, 세포 골격유지에 관여하는 등 세포 신호체계에서 핵심 역할을 하는 효소이다. PI3K는 세 그룹으로 나누어지며 type I PI3K는 leukocyte에서 우선적으로 발현되고 G-proteins의 ${eta}{gamma}$ subunits에 의해서 활성화 된다. 본 연구에서는 넙치(Paralichthys olivaceus)의 $PI3K{gamma}$를 암호화하는 cDNA를 클로닝하였다. 넙치의 $PI3K{gamma}$는 1,341 bp 염기로 구성되는 한 개의 ORF를 가지며 이 단백질은 447 아미노산으로 구성되어있다. $PI3K{gamma}$는 zebrafish의 $PI3K{gamma}$와 89.6%, mouse와는 84.7%, Norway rat와는 84%, human의 $PI3K{gamma}$와는 74.9%가 아미노산 상동성을 나타내었다. $PI3K{gamma}$유전자의 대장균에서 발현을 위하여 pET-44a(+)-PI3K 재조합 DNA를 구축하여 대장균에서 발현시킨 결과 49 kDa의 재조합 단백질이 과발현 됨을 확인 할 수 있었다. His-tag affinity chromatography를 이용하여 $PI3K{gamma}$단백질을 순순 분리하였으며 wortmannin을 이용하여 $PI3K{gamma}$의 활성을 분석하였다.
Phosphoinositide 3-kinase (PI3K) plays a central role in cell signaling and leads to cell proliferation, survival, motility, exocytosis, and cytoskeletal rearrangements, as well as specialized cell responses, superoxide production, and cardiac myocyte growth. PI3K is divided into three classes; type I PI3K is preferentially expressed in leukocytes and activated by ${eta}{gamma}$ subunits of heterotrimeric G-proteins. In this study, the cDNAs encoding the $PI3K{gamma}$ gene were isolated from a brain cDNA library constructed using the flounder (Paralichthys olivaceus). The sequence of the isolated $PI3K{gamma}$ was 1341 bp, encoding 447 amino acids. The nucleotide sequence of the $PI3K{gamma}$ gene was analyzed with that of other species, including Oreochromis niloticus and Danio rerio, and it turned out to be well conserved during evolution. The $PI3K{gamma}$ gene was subcloned into the expression vector pET-44a(+), and expressed in the E. coli BL21 (DE3) codon plus cell. The resulting protein was expressed as a fusion protein of approximately 49 kDa containing a C-terminal six-histidine extension that was derived from the expression vector. The expressed protein was purified to homogeneity by His-tag affinity chromatography and showed enzymatic activity corresponding to $PI3K{gamma}$. The binding of wortmannin to $PI3K{gamma}$, as detected by anti-wortmannin antisera, closely followed the inhibition of the kinase activities. The results obtained from this study will provide a wider base of knowledge on the primary structure and characterization of the $PI3K{gamma}$ at the molecular level.
