Function of MEKK3 and its osmosensing scaffold protein

描述（由申请人提供）：MEKK3是一种调节p38和ERK5 MAPK通路的map3激酶。鉴定出一种结合MEKK3的支架蛋白，命名为MEKK3或OSM的渗透传感支架。OSM被定义为人类疾病脑海绵状血管瘤（CCM）中的一种基因突变。家族性CCM是一种遗传性微血管疾病，导致患者中枢神经系统毛细血管扩张、渗漏。CCM基因座定位到Krit （ccm1）、OSM （ccm2）和PDCD10 （ccm3）三个基因。我们已经证明OSM (CCM2), KRIT （CCM1）和PDCD10 （CCM3）在遗传上是相同的途径，并在生物化学上形成一个复合物，表明它们协同工作。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，可组织更大的蛋白质复合物，而CCM3预计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蛋白复合物控制内皮细胞生理的功能和时空调节。该建议的假设是，CCM蛋白复合物是动态的，其组成和亚细胞位置随时空变化而变化。CCM1-CCM2-CCM3复合物既存在于细胞质中，也存在于片状足样膜突起中。此外，CCM2快速进出细胞核，并作为核细胞质穿梭蛋白发挥作用。CCM1也可以在细胞核中发现，CCM2的过表达将CCM1重新分配到细胞质中，这表明CCM1-CCM2的相互作用改变了CCM1在细胞中的定位（细胞核与细胞质），表明CCM2可能将CCM1运送出细胞核。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复合物的一部分，CCM1的动态调控似乎是维持中枢神经系统微血管完整性所必需的。公共卫生相关性：CCM是一种由调节血管内皮细胞功能的编码蛋白基因突变引起的疾病。CCM影响了美国约0.5%的人口，是出血性休克的主要潜在病理。本研究的目的是了解血管内皮细胞中CCM蛋白复合物的调控和功能，这将有助于了解CCM的潜在病理，并为治疗和预防CCM提供潜在的新治疗策略。

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.