Function of MEKK3 and its osmosensing scaffold protein

描述(申请人提供)：MEKK3是一种MAP3K，调节p38和ERK5 MAPK通路。鉴定了一种与MEKK3结合的支架蛋白，命名为MEKK3渗透敏感支架或OSM。OSM被定义为人类疾病脑海绵状血管畸形(CCM)中的一种突变基因。家族性CCM是一种遗传性微血管疾病，可导致患者中枢神经系统毛细血管扩张、渗漏。CCM基因定位于3个基因：KRIT(Ccm1)、osm(Ccm2)和PDCD10(Ccm3)。我们已经证明了OSM(CCM2)、KRIT(CCM1)和PDCD10(CCM3)在基因上是相同的途径，并且在生化上形成了一个复合体，这表明它们是协同工作的。CCM1、2和3似乎没有可识别的催化结构域。CCM1和CCM2是支架样蛋白质，组成一个更大的蛋白质复合体，而CCM3被预测具有蛋白质接头样功能。我们的研究将在机制水平上定义CCM蛋白复合体的功能和时空调节，以控制内皮细胞的生理。这一提议的假设是，CCM蛋白质复合体是动态的，在组成和亚细胞位置上有时空变化。CCM1-CCM2-CCM3复合体定位于细胞质和片状脂膜突起中。此外，CCM2快速进出细胞核，并作为核质穿梭蛋白发挥作用。CCM1也存在于细胞核中，CCM2的过度表达使CCM1重新分布到细胞质中，表明CCM1与CCM2的相互作用改变了CCM1在细胞内的定位(核内与胞浆中)，提示CCM2可能将CCM1穿梭出细胞核。CCM1(KRIT)可以靶向内皮细胞紧密连接，调节紧密连接的完整性。因此，作为CCM1-CCM2-CCM3复合体一部分的CCM1的动态调节似乎是维持中枢神经系统微血管完整性所必需的。与公共卫生相关：CCM是一种由编码调节血管内皮细胞功能的蛋白质的基因突变引起的疾病。CCM影响美国约0.5%的人口，是出血性打击的主要潜在病理。本研究的目的是了解CCM蛋白复合体在血管内皮细胞中的调节和功能，从而有助于了解CCM的潜在病理机制，并为治疗和预防提供潜在的新的治疗策略。

DESCRIPTION (provided by applicant): MEKK3 is a MAP3kinase that regulates the p38 and ERK5 MAPK pathways. A scaffolding protein was identified that binds MEKK3, named osmosensing scaffold for MEKK3 or OSM. OSM has been defined as a gene mutated in the human disease cerebral cavernous malformations (CCM). Familial CCM is a hereditary microvascular disorder that results in the formation of dilated, leaky capillaries in the central nervous system of affected individuals. Loci for CCM were mapped to three genes, Krit (ccm1), OSM (ccm2) and PDCD10 (ccm3). We have shown that OSM (CCM2), KRIT (CCM1) and PDCD10 (CCM3) are genetically in the same pathway and biochemically form a complex, indicating that they work in concert. CCM1, 2 and 3 appear to have no identifiable catalytic domains. CCM1 and CCM2 are scaffold-like proteins organizing a larger protein complex while CCM3 is predicted to have protein adaptor-like function. Our studies will define at a mechanistic level the function and spatio-temporal regulation of the CCM protein complex for the control of endothelial cell physiology. The hypothesis for this proposal is that the CCM protein complex is dynamic with spatio-temporal changes in composition and subcellular location. CCM1-CCM2-CCM3 complexes are localized both in the cytoplasm and in lamellipodia-like membrane protrusions. In addition, CCM2 rapidly transients in and out of the nucleus and functions as a nucleocytoplasmic shuttling protein. CCM1 can also be found in the nucleus and CCM2 overexpression redistributes CCM1 to the cytoplasm, indicating the CCM1-CCM2 interaction alters the localization of CCM1 in the cell (nuclear versus cytoplasmic), suggesting CCM2 may shuttle CCM1 out of the nucleus. CCM1 (KRIT) can target to endothelial cell tight junctions and regulate tight junction integrity. Thus, the dynamic regulation of CCM1 as part of the CCM1-CCM2-CCM3 complex appears required for the maintenance of microvascular integrity in the CNS. PUBLIC HEALTH RELEVANCE: CCM is a disease caused by mutation of genes encoding proteins that regulate the function of vascular endothelial cells. CCM affects approximately 0.5% of the population in the United States and is a major underlying pathology for hemorrhagic strike. The goal of this proposal is to understand the regulation and function of the CCM protein complex in vascular endothelial cells, which will lead to an understanding of the underlying pathology of CCM and provide potential new therapeutic strategies for cure and prevention.