Function of Protein Kinase PASK enriched in Transporting Epithelia

PASK是一种与ste20相关的蛋白激酶，富集于肾上腺带肾小球细胞和转运上皮细胞，如脑脉络丛和胃壁细胞。本研究对PASK的分子功能和生理作用进行了研究，得到以下结果：PASK在体内结合肌动蛋白和微管蛋白，在其激酶结构域具有f -肌动蛋白结合活性。在培养细胞中，PASK在热休克和高超声速NaCl等细胞应激刺激下从细胞质转移到细胞骨架。这些结果表明，PASK在细胞应激反应过程中参与了细胞骨架的调节。当细胞暴露于细胞应激时，c端非催化结构域与细胞骨架结合，而激酶结构域与细胞骨架结合，无论细胞是否暴露于细胞应激。这些结果表明，PASK通过其激酶结构域与肌动蛋白结合，并通过c端结构域通过非肌动蛋白与细胞骨架结合。通过靶向破坏PASK基因产生的PASK缺陷小鼠的生育能力下降，生殖器官出现异常：PASK缺陷雄性的睾丸大小为正常的77%，突变雌性的子宫比野生型大2- 3倍。不育突变雄性的部分精管不含精子，而这种小管在可育突变体中很少见。这些结果表明PASK参与了生殖。PASK缺失影响生殖的机制，包括突变生殖器官异常的原因，目前正在该实验室进行研究。

PASK is a Ste20-related protein kinase enriched in adrenal zona glomerulosa cells and transporting epithelia such as brain choroid plexus and gastric parietal cells. The molecular function and physiological roles of PASK have been investigated in this study, and we have obtained the following results :1. PASK associates actin and tubulin in vivo, and in its kinase domain has F-actin-binding activity. In cultured cells, PASK translocates from the cytosol to cytoskeleton upon stimulation by cellular stresses like heat shock and hypersonic NaCl. These results suggest that PASK is involved in the regulation of cytoskeleton during responses to cellular stresses.The C-terminal non-catalytic domain binds cytoskeleton when cells are exposed to celluar stresses, while the kinase domain binds cytoskeleton regardless exposure to the celluar stresses. These results suggest that PASK binds cytoskeleton through its kinase domain to actin cytoskeleton and through the C-terminal domain to cytoskeleton via non-actin protein(s).2. PASK-deficient mice generated by targeted disruption of the PASK gene exhibit reduced fertility and shows anomalies in the reproductive organs : PASK deficient males have testes that were 77 % of the normal size and the uterine of mutant females is 2- to 3-fold larger than the wild-type. Portions of the seminiferous tubules of sterile mutant males contain no spermatids, while such tubules are rare in the fertile mutants. These results suggest that PASK is involved in the reproduction. The mechanisms by which PASK deletion affects the reproduction, including the cause of anomalies in the mutant reproductive organs, are currently under investigation in this laboratory.