GLOMERULAR LAMININS: STRUCTURE AND FUNCTION

描述(改编自《研究人员摘要》)：层粘连蛋白(LN)是一种大的 异三聚体细胞外基质糖蛋白在 细胞的黏附、增殖、迁移、收缩和分化。每个人 肾小球细胞类型表达一组独特的LM亚型。时态 它们表达的开关与过程中的形态转变相关 肾小球形成。在某些情况下，细胞分化的启动或 细胞表型的维持与一种特殊的Lm亚型有关。 肾小球系膜细胞(MC)表达LM-8(A1B1g1)，它与entactin结合， 交叉连接到纤维状细胞外基质，促进附着 并在传播。MC也表达LM-9(A1B1g1)，它仍然定位于 细胞表面的离散区域，并启动丝状足的形成。这 提案将进一步描述LM亚型直接引导MC的机制 功能。在第一个具体目标中，我们提出了LMa4链形成一个 与丝氨酸-1(肌动蛋白结合蛋白280)的复合体，其功能是产生 MC在收缩过程中的受力和机械保护。因为这个建筑群是 与肠道中的血管平滑肌细胞和平滑肌细胞一样，我们 提出它是一种相当于 LMa2-dystrocan-dystrophin复合体是骨骼肌所必需的 伸缩性。MC表达的两种Lm亚型对B的用法不同 链；因此，它们很可能还与MC表面上的蛋白质结合， 传达额外的功能特性。拟议的实验将确定 这些络合物中的分子伙伴。第二个具体目标的目标 是定义介导MC收缩的LM受体复合体和 迁移。在对各种刺激的生物反应中，蛋白酶是 释放产生特定的LM片段的病毒。在某些情况下，这些碎片 获得新的生物活动。初步数据显示，LM的一个片段 B1链被转移到细胞核，在那里它调节基因的表达。它 第三个具体目标的目标是确认这些观察结果和 阐明LMB1在细胞核中的作用机制。进展性肾小球 老年性肾小球硬化和糖尿病肾病等疾病 以LM亚型表达的变化为特征的。进一步澄清 在LM亚型调节MC收缩能力的机制中， 保护毛细血管壁不会过度扩张，在伤口愈合期间迁移， 维持正常的细胞表型和功能应该提供重要的 对疾病发病机制的洞察。

DESCRIPTION (Adapted from Investigator's Abstract): Laminin (LM) is a large heterotrimeric extracellular matrix glycoprotein that plays important roles in cell adhesion, proliferation, migration, contraction, and differentiation. Each glomerular cell type expresses a unique subset of LM isoforms. Temporal switches in their expression correlate with morphologic transitions during glomerulogenesis. In some cases, initiation of cellular differentiation or maintenance of cellular pheontype has been linked to a particular LM isoform. Glomerular mesangial cells (MC) express LM-8 (a1B1g1), which binds entactin, cross-links into the fibrillar extracellular matrix and facilitates attachment and spreading. MC also express LM-9 (a1B1g1), which remains localized to discrete regions on the cell surface and initiates filopodia formation. This proposal will further characterize the mechanisms whereby LM isoforms direct MC function. In the first specific aim, we propose that the LMa4 chain forms a complex with filamin-1 (actin binding protein 280) that functions to generate force and mechano-protection of MC during contraction. Because this complex is shared with vascular smooth muscle cells and smooth muscle in the intestine, we propose that it is the smooth muscle equivalent of the LMa2-dystroglycan-dystrophin complex that is required for skeletal muscle contractility. The two LM isoforms expressed by MC differ in their use of B chains; thus it is likely that they also engage proteins on the MC surface that convey additional specificity of function. Proposed experiments will identify the molecular partners in these complexes. The goal of the second specific aim is to define the LM-receptors complexes that mediate MC contraction and migration. During biologic responses to a variety of stimuli, proteases are released that generate specific fragments of LM. In some cases these fragments acquire new biologic activity. Preliminary data show that a fragment of the LM B1 chain is translocated to the nucleus where it regulates gene expression. It is the goal of the third specific aim to confirm these observations and elucidate mechanisms whereby LMB1 acts in the nucleus. Progressive glomerular diseases such as glomerulosclerosis of aging and diabetic nephropathy are characterized by changes in the expression of LM isoforms. Further elucidation of the mechanisms whereby LM isoforms modulate the MC capacity to contract, protect the capillary wall from over distention, migrate during wound healing, and maintain normal cellular phentype and function should provide important insights into disease pathogenesis.