Holst L S, Mulder H, Manganiello V, Sundler F, Ahrén B, Holm C, Degerman E
Department of Cell and Molecular Biology, Lund University, Lund, Sweden.
Biochem Biophys Res Commun. 1998 Sep 8;250(1):181-6. doi: 10.1006/bbrc.1998.9166.
Protein kinase B (PKB) is involved in signaling to a multitude of important cellular events and is activated by insulin and growth factors, including insulin-like growth factor I (IGF-I). We show here expression of PKB in pancreatic islets and in the beta cell lines HIT-T15, INS-1, and RINm5F. Expression of PKB mRNA and the presence of PKB isoforms (alpha, beta, and gamma) were assessed by Northern blot analysis and RT-PCR, respectively. Antibodies recognizing different parts of PKB isoforms were employed to demonstrate PKB protein expression by immunoblot analysis. By use of immunohistochemistry in rat and mouse pancreatic tissue sections, PKB was localized to predominantly beta cells. Regulation of PKB was examined in INS-1 and RINm5F cells; upon stimulation with IGF-I (5-10 min), PKB was phosphorylated and activated (approximately 3-fold) by a wortmannin-sensitive mechanism, indicating involvement of phosphatidylinositol-3 kinase. The possible participation of PKB in signal transduction pathways modulating cAMP-dependent insulin secretion and in proliferation of beta cells is discussed.
蛋白激酶B（PKB）参与众多重要细胞事件的信号传导，可被胰岛素和生长因子激活，包括胰岛素样生长因子I（IGF-I）。我们在此展示了PKB在胰岛以及β细胞系HIT-T15、INS-1和RINm5F中的表达情况。分别通过Northern印迹分析和逆转录聚合酶链反应（RT-PCR）评估了PKB mRNA的表达以及PKB同工型（α、β和γ）的存在情况。利用识别PKB同工型不同部位的抗体，通过免疫印迹分析来证明PKB蛋白的表达。通过对大鼠和小鼠胰腺组织切片进行免疫组织化学分析，发现PKB主要定位于β细胞。在INS-1和RINm5F细胞中检测了PKB的调节情况；用IGF-I刺激（5 - 10分钟）后，PKB通过一种渥曼青霉素敏感机制发生磷酸化并被激活（约3倍），这表明磷脂酰肌醇-3激酶参与其中。本文还讨论了PKB在调节环磷酸腺苷（cAMP）依赖性胰岛素分泌的信号转导途径以及β细胞增殖中可能的参与情况。
