Centrosomal P4.1-associated protein (CPAP) plays a critical role in restricting the centriole length in human cells. Here, we report a novel, positive regulatory role for CPAP in endocytic vesicular transport (EVT) and lysosome targeting of internalized-cell surface receptor EGFR. We observed that higher CPAP levels cause an increase in the abundance of multi-vesicular body (MVB) and EGFR is detectable in CPAP-overexpression induced puncta. While the surface levels, and total and phosphorylated cellular levels of EGFR are higher under CPAP deficiency, ligand-engagement induced internalization of this receptor is not impacted by CPAP levels. Furthermore, routing of EGFR into early endosomes is not influenced by CPAP. However, most importantly, we found that CPAP is required for targeting ligand-activated, internalized EGFR to lysosome. Transport of ligand-bound EGFR from early endosome to late endosome/MVB and lysosome is severely diminished in CPAP-depleted cells. Moreover, CPAP depleted cells showed diminished ability to form MVB structures upon EGFR activation. These observations show a positive regulatory role for CPAP in early endosome to late endosome transport and lysosome targeting of ligand-bound EGFR-like cell surface receptors. Overall, identification of this regulatory role for CPAP in endocytic trafficking of EGFR provides new insights in understanding the cellular functions of CPAP.

中文翻译：

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中心体P4.1相关蛋白（CPAP）积极调节EGFR的内吞水泡运输和溶酶体靶向

中心体P4.1相关蛋白（CPAP）在限制人类细胞的中心粒长度方面起着关键作用。在这里，我们报告了CPAP在内吞性细胞表面受体EGFR的内吞囊泡运输（EVT）和溶酶体靶向中的新型积极调控作用。我们观察到较高的CPAP水平会导致多囊泡体（MVB）含量增加，并且在CPAP过表达诱导的泪点中可检测到EGFR。在CPAP缺乏的情况下，尽管EGFR的表面水平，总细胞水平和磷酸化细胞水平较高，但配体结合诱导的该受体的内在化不受CPAP水平的影响。此外，EGFR进入早期内体的途径不受CPAP影响。然而，最重要的是，我们发现CPAP是将配体激活的内在化EGFR靶向溶酶体所必需的。在耗尽CPAP的细胞中，配体结合的EGFR从早期内体向晚期内体/ MVB和溶酶体的转运严重减少。此外，耗尽CPAP的细胞在EGFR激活后显示出形成MVB结构的能力减弱。这些观察结果表明，CPAP在早期内体到晚期内体运输和溶酶体靶向配体结合的EGFR样细胞表面受体中发挥积极的调节作用。总体而言，对CPAP在EGFR内吞运输中的这种调节作用的鉴定为了解CPAP的细胞功能提供了新的见解。这些观察结果表明，CPAP在早期内体到晚期内体运输和溶酶体靶向配体结合的EGFR样细胞表面受体中发挥积极的调节作用。总体而言，对CPAP在EGFR内吞运输中的这种调节作用的鉴定为了解CPAP的细胞功能提供了新的见解。这些观察结果表明，CPAP在早期内体到晚期内体运输和溶酶体靶向配体结合的EGFR样细胞表面受体中发挥积极的调节作用。总体而言，对CPAP在EGFR内吞运输中的这种调节作用的鉴定为了解CPAP的细胞功能提供了新的见解。