Lasp-1 is a regulated phosphoprotein within the cAMP signaling pathway in the gastric parietal cell
Lasp-1 is a regulated phosphoprotein within the cAMP signaling pathway in the gastric parietal cell
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DOI：
10.1152/ajpcell.1998.275.1.c56
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发表时间：
1998-07-01
影响因子：
5.5
通讯作者：
Chen, X
中科院分区：
文献类型：
--
作者：
Chew, CS;Parente, JA;Chen, X
cAMP信号通路的激活与包括胃壁细胞在内的多种细胞类型中的分泌相关事件增加相关。在该途径中，以及在其他细胞内信号传导途径中，蛋白质磷酸化充当主要下游调节机制。然而，虽然激动剂和cAMP依赖性激活cAMP依赖性蛋白激酶（PKA）已被证明，目前知之甚少的下游体内磷蛋白底物的这种酶。在这里，我们报告的分离，微测序和克隆的LIM和SH 3结构域包含，cAMP反应，40 kDa磷蛋白（pp 40）从兔胃壁细胞。pp 40的推导氨基酸序列为93.5%，与人类基因lasp-1的推定蛋白产物同源，这是最近确定的基础上，它在一些乳腺癌中的过度表达。除了LIM和SH 3结构域，兔同源物还含有两个高度保守的PKA共有序列以及两个保守的SH 2结合基序和几个其他推定的蛋白激酶磷酸化位点，包括两个酪氨酸激酶。结合北方和Western印迹分析表明，pp 40/lasp-1广泛表达（通过一个单一的3.3 kb的信息），不仅在上皮组织，而且在肌肉和大脑。此外，用腺苷酸环化酶激活剂毛喉素刺激分离的壁细胞、远端结肠隐窝和胰腺细胞导致出现更高分子量形式的pp 40/lasp-1，这一发现与蛋白磷酸化的增加一致。因此，pp 40/lasp-l似乎在广泛的上皮细胞类型中在cAMP信号传导途径内被调节。由于cAMP依赖性的pp 40磷酸化的增加与壁细胞中的分泌反应相关，并且由于pp 40似乎广泛分布于各种分泌组织中，因此这种新定义的信号蛋白可能在调节许多不同细胞类型中的离子转运或其他分泌相关活动中发挥重要作用。
Activation of the cAMP signaling pathway is correlated with increased secretory-related events in a wide variety of cell types including the gastric parietal cell. Within this pathway, as well as in other intracellular signaling pathways, protein phosphorylation serves as a major downstream regulatory mechanism. However, although agonist and cAMP-dependent activation of cAMP-dependent protein kinase (PKA) has been demonstrated, little is currently known about the downstream in vivo phosphoprotein substrates of this enzyme. Here we report the isolation, microsequencing, and cloning of a LIM and SH3 domain-containing, cAMP-responsive, 40-kDa phosphoprotein (pp40) from rabbit gastric parietal cells. The deduced amino acid sequence for pp40 is 93.5%, homologous with the putative protein product of the human gene lasp-1, which was recently identified based on its overexpression in some breast carcinomas. In addition to LIM and SH3 domains, the rabbit homolog contains two highly conserved PKA consensus sequences as well as two conserved SH2 binding motifs and several other putative protein kinase phosphorylation sites, including two for tyrosine kinase(s). Combined Northern and Western blot analyses indicate that pp40/lasp-1 is widely expressed (through a single 3.3-kb message) not only in epithelial tissues but also in muscle and brain. Furthermore, stimulation of isolated parietal cells, distal colonic crypts, and pancreatic cells with the adenylyl cyclase activator forskolin leads to the appearance of a higher molecular weight form of pp40/lasp-1, a finding which is consistent with an increase in protein phosphorylation. Thus pp40/lasp-l appears to be regulated within the cAMP signaling pathway in a wide range of epithelial cell types. Because the cAMP-dependent increase in pp40 phosphorylation is correlated with secretory responses in the parietal cell and because pp40 appears to be widely distributed among various secretory tissues, this newly defined signaling protein may play an important role in modulating ionic transport or other secretory-related activities in many different cell types.