The human SH3 domain Binding Glutamic acid Rich Like 3 (SH3BGRL3) gene is highly conserved in phylogeny and widely expressed in human tissues. However, its function is largely undetermined. The protein was found to be overexpressed in several tumors, and recent work suggested a possible relationship with EGFR family members. We aimed at further highlighting on these issues and investigated SH3BGRL3 molecular interactions and its role in cellular migration ability. We first engineered the ErbB2-overexpressing SKBR3 cells to express exogenous SH3BGRL3, as well as wild type Myo1c or different deletion mutants. Confocal microscopy analysis indicated that SH3BGRL3 co-localized with Myo1c and ErbB2 at plasma membranes. However, co-immunoprecipitation assays and mass spectrometry demonstrated that SH3BGRL3 did not directly bind ErbB2, but specifically recognized Myo1c, on its IQ-bearing neck region. Importantly, the interaction with Myo1c was Ca2+-dependent. A role for SH3BGRL3 in cell migration was also assessed, as RNA interference of SH3BGRL3 in MDA-MB-231 cells, used as a classical migration model, remarkably impaired the migration ability of these cells. On the other side, its over-expression increased cell motility. The results of this study provide insights for the formulation of novel hypotheses on the putative role of SH3BGRL3 protein in the regulation of myosin-cytoskeleton dialog and in cell migration. It could be envisaged the SH3BGRL3-Myo1c interaction as a regulation mechanism for cytoskeleton dynamics. It is well known that, at low Ca2+ concentrations, the IQ domains of Myo1c are bound by calmodulin. Here we found that binding of Myo1c to SH3BGRL3 requires instead the presence of Ca2+. Thus, it could be hypothesized that Myo1c conformation may be modulated by Ca2+-driven mechanisms that involve alternative binding by calmodulin or SH3BGRL3, for the regulation of cytoskeletal activity.

中文翻译：

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SH3BGRL3 以钙依赖性方式与肌球蛋白 1c 结合并调节 MDA-MB-231 细胞系中的迁移

人类 SH3 域结合谷氨酸富集 Like 3 (SH3BGRL3) 基因在系统发育中高度保守并在人体组织中广泛表达。然而，其功能在很大程度上尚未确定。发现该蛋白质在几种肿瘤中过度表达，最近的工作表明可能与 EGFR 家族成员有关。我们旨在进一步强调这些问题并研究了 SH3BGRL3 分子相互作用及其在细胞迁移能力中的作用。我们首先设计了过表达 ErbB2 的 SKBR3 细胞以表达外源性 SH3BGRL3，以及野生型 Myo1c 或不同的缺失突变体。共聚焦显微镜分析表明 SH3BGRL3 在质膜上与 Myo1c 和 ErbB2 共定位。然而，免疫共沉淀分析和质谱证明 SH3BGRL3 不直接结合 ErbB2，但在其承载 IQ 的颈部区域特别识别了 Myo1c。重要的是，与 Myo1c 的相互作用是 Ca2+ 依赖性的。还评估了 SH3BGRL3 在细胞迁移中的作用，因为 SH3BGRL3 在 MDA-MB-231 细胞中的 RNA 干扰，用作经典迁移模型，显着削弱了这些细胞的迁移能力。另一方面，它的过度表达增加了细胞运动性。这项研究的结果为制定关于 SH3BGRL3 蛋白在调节肌球蛋白-细胞骨架对话和细胞迁移中的假定作用的新假设提供了见解。可以将 SH3BGRL3-Myo1c 相互作用视为细胞骨架动力学的调节机制。众所周知，在低 Ca2+ 浓度下，Myo1c 的 IQ 结构域受钙调蛋白结合。在这里，我们发现 Myo1c 与 SH3BGRL3 的结合需要 Ca2+ 的存在。因此，可以假设 Myo1c 构象可能受 Ca2+ 驱动机制的调节，该机制涉及钙调蛋白或 SH3BGRL3 的替代结合，以调节细胞骨架活性。