Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
J Cell Sci. 2010 Dec 1;123(Pt 23):4128-44. doi: 10.1242/jcs.072041. Epub 2010 Nov 9.
In common with other p120-catenin subfamily members, Xenopus ARVCF (xARVCF) binds cadherin cytoplasmic domains to enhance cadherin metabolic stability or, when dissociated, modulates Rho-family GTPases. We report here that xARVCF binds and is stabilized by Xenopus KazrinA (xKazrinA), a widely expressed conserved protein that bears little homology to established protein families, and which is known to influence keratinocyte proliferation and differentiation and cytoskeletal activity. Although we found that xKazrinA binds directly to xARVCF, we did not resolve xKazrinA within a larger ternary complex with cadherin, nor did it co-precipitate with core desmosomal components. Instead, screening revealed that xKazrinA binds spectrin, suggesting a potential means by which xKazrinA localizes to cell-cell borders. This was supported by the resolution of a ternary biochemical complex of xARVCF-xKazrinA-xβ2-spectrin and, in vivo, by the finding that ectodermal shedding followed depletion of xKazrin in Xenopus embryos, a phenotype partially rescued with exogenous xARVCF. Cell shedding appeared to be the consequence of RhoA activation, and thereby altered actin organization and cadherin function. Indeed, we also revealed that xKazrinA binds p190B RhoGAP, which was likewise capable of rescuing Kazrin depletion. Finally, xKazrinA was found to associate with δ-catenins and p0071-catenins but not with p120-catenin, suggesting that Kazrin interacts selectively with additional members of the p120-catenin subfamily. Taken together, our study supports the essential role of Kazrin in development, and reveals the biochemical and functional association of KazrinA with ARVCF-catenin, spectrin and p190B RhoGAP.
与其他 p120 连环蛋白亚家族成员一样，非洲爪蟾 ARVCF（xARVCF）结合钙粘蛋白胞质结构域以增强钙粘蛋白的代谢稳定性，或者在解离时调节Rho 家族 GTP 酶。我们在这里报告，xARVCF 与广泛表达的保守蛋白 Xenopus KazrinA（xKazrinA）结合并稳定，该蛋白与已建立的蛋白家族几乎没有同源性，已知其影响角质形成细胞增殖和分化以及细胞骨架活性。虽然我们发现 xKazrinA 直接结合 xARVCF，但我们没有解析出更大的钙粘蛋白三元复合物中的 xKazrinA，也没有与核心桥粒成分共沉淀。相反，筛选表明 xKazrinA 与 spectrin 结合，这表明 xKazrinA 定位到细胞-细胞边界的一种潜在方式。这得到了 xARVCF-xKazrinA-xβ2-spectrin 三元生化复合物的解析的支持，并且在体内，通过在外胚层脱落中发现 Xenopus 胚胎中 xKazrinA 的耗竭，该表型部分被外源 xARVCF 挽救的发现得到了支持。细胞脱落似乎是 RhoA 激活的结果，从而改变了肌动蛋白组织和钙粘蛋白功能。事实上，我们还揭示了 xKazrinA 与 p190B RhoGAP 结合，后者同样能够挽救 Kazrin 耗竭。最后，发现 xKazrinA 与 δ-catenin 和 p0071-catenin 结合，但不与 p120-catenin 结合，这表明 Kazrin 选择性地与 p120 连环蛋白亚家族的其他成员相互作用。总之，我们的研究支持 Kazrin 在发育中的重要作用，并揭示了 KazrinA 与 ARVCF-catenin、spectrin 和 p190B RhoGAP 的生化和功能关联。
