Rac1 and the actin cytoskeleton in renal tubular repair

Rac1 和肌动蛋白细胞骨架在肾小管修复中的作用

• 批准号: 10739610
• 负责人: Fabian Maximilian Bock
• 金额: $ 16万
• 依托单位: VANDERBILT UNIVERSITY MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2028-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10739610
• 关键词: 3-Dimensional; Actins; Actomyosin; Acute Renal Failure with Renal Papillary Necrosis; Architecture; Biological Process; CDC2 gene; Cell Cycle; Cell Cycle Regulation; Cell Death; Cell Proliferation; Cell Shape; Cell division; Cell membrane; Cells; Cellular Morphology; Chronic Kidney Failure; Complex; Cyclin B; Cytoskeleton; Data; Defect; Development; Duct (organ) structure; Ductal Epithelium; ERM protein; Electrolytes; Epithelial Cells; Epithelium; G2/M Transition; Histologic; Homeostasis; In Vitro; Injury; Ischemia; Kidney; Kidney Diseases; Knowledge; Lead; M cell; Mechanics; Mediating; Mitosis; Mitotic; Modeling; Molecular; Morphology; Natural regeneration; Nutrient; Obstruction; Optics; Phosphotransferases; Play; Process; Proliferating; Proteins; Reperfusion Therapy; Resolution; Role; Shapes; Testing; Tissues; Tube; Tubular formation; Water; Work; epithelial repair; epithelium regeneration; high resolution imaging; in vivo; kidney repair; live cell imaging; molecular dynamics; mutant; new therapeutic target; novel; p21 activated kinase; renal epithelium; repaired; rho GTP-Binding Proteins; tissue repair

Polarized epithelial tubes are critical for an intact kidney. They control water, electrolyte, and nutrient homeostasis, all of which are deranged in chronic kidney disease. These specialized epithelia require a highly organized actin cytoskeleton that determines cellular shape and function. During renal epithelial repair, the actin cytoskeleton of proliferating cells is rapidly re-organized to form the complex polarized architecture of an epithelial tube. The small Rho GTPase Rac1 is a multifunctional molecular switch and a master regulator of the actin cytoskeleton. We recently demonstrated that Rac1 is required to maintain actin cytoskeletal integrity, epithelial polarity, and cell shape of the mature collecting duct (CD) epithelium. It is still unknown how the actin cytoskeleton is regulated in epithelial cell repair and what role Rac1 plays in this process. For coordinated epithelial tube regeneration, epithelial cells need to rapidly progress through the cell cycle and divide in the correct direction along the tissue plane by undergoing oriented mitosis. A critical step in renal epithelial repair is the activation of the master mitotic kinase cyclin B–CDK1 complex which drives the G2/M transition and prepares the actin cytoskeleton for mitosis. Undergoing mitosis correctly in a confined tight epithelial space is a challenging process, which requires the cells to round up against their neighbors. This so-called mitotic rounding depends on the actin cytoskeleton forming a dense contractile actomyosin cortex, which is tethered to the cell membrane by ERM Proteins (Ezrin), a known target of Rac1 and its main effector p21-activated kinase (Pak1). Defects in mitotic morphology lead to cell cycle delays, mechanical defects, and cell death and abnormal repair. How actin cytoskeletal dynamics are molecularly coordinated and by what means cell shape is connected to cell cycle control during these critical biological processes in kidney repair is not known. We deleted Rac1 in the collecting duct (AQP2Cre) or proximal tubule (γGTCre) and performed reversible unilateral ureteric obstruction (R-UUO) or ischemia-reperfusion induced acute kidney injury (AKI-IRI). Functional and histological assessment indicated that Rac1 is required for repair in both models. Optical clearing and 3D high-resolution imaging revealed that the mutant epithelium was unable to restore normal morphology and actin organization post-injury. Repair in Rac1 mutants showed defects in actin-dependent mitotic morphology, misplaced mitotic figures, and the inability to proliferate due to a G2/M cell cycle defect. 3D high-resolution live imaging of cell division in vitro revealed that Rac1 is required for normal mechanical progression of mitosis and Ezrin-associated mitotic rounding in renal epithelial cells. This forms the basis for our hypothesis that Rac1 controlled actin-dependent mitotic rounding mediated via its effector Pak1 and the linker protein Ezrin is required to promote cell cycling during tissue repair, which will be tested in the following aims. Aim 1: Define the mechanisms whereby Rac1 regulates renal epithelial repair in vivo. Aim 2: Define the mechanism whereby Rac1 controls renal epithelial mitotic morphology in vitro.

极化上皮管对完整的肾脏至关重要。它们控制着水、电解质和营养