IEOS Istituto di Endocrinologia e Oncologia Sperimentale "G. Salvatore", National Council of Research, Napoli, Italy.
Department of Molecular Medicine and Medical Biotechnologies, University "Federico II", Napoli, Italy.
J Cell Physiol. 2016 Aug;231(8):1695-708. doi: 10.1002/jcp.25267. Epub 2015 Dec 10.
Rab7 regulates the biogenesis of late endosomes, lysosomes, and autophagosomes. It has been proposed that a functional and physical interaction exists between Rab7 and Rac1 GTPases in CDH1 endocytosis and ruffled border formation. In FRT cells over-expressing Rab7, increased expression and activity of Rac1 was observed, whereas a reduction of Rab7 expression by RNAi resulted in reduced Rac1 activity, as measured by PAK1 phosphorylation. We found that CDH1 endocytosis was extremely reduced only in Rab7 over-expressing cells but was unchanged in Rab7 silenced cells. In Rab7 under or over-expressing cells, Rab7 and LC3B-II co-localized and co-localization in large circular structures occurred only in Rab7 over-expressing cells. These large circular structures occurred in about 10% of the cell population; some of them (61%) showed co-localization of Rab7 with cortactin and f-actin and were identified as circular dorsal ruffles (CDRs), the others as mature autophagosomes. We propose that the over-expression of Rab7 is sufficient to induce CDRs. Furthermore, in FRT cells, we found that the expression of the insoluble/active form of Rab7, rather than Rab5, or Rab8, was inducible by cAMP and that cAMP-stimulated FRT cells showed increased PAK1 phosphorylation and were no longer able to endocytose CDH1. Finally, we demonstrated that Rab7 over-expressing cells are able to endocytose exogenous thyroglobulin via pinocytosis/CDRs more efficiently than control cells. We propose that the major thyroglobulin endocytosis described in thyroid autonomous adenomas due to Rab7 increased expression, occurs via CDRs. J. Cell. Physiol. 231: 1695-1708, 2016. © 2015 Wiley Periodicals, Inc.
Rab7 调节晚期内涵体、溶酶体和自噬体的生物发生。有人提出，Rab7 和 Rac1 GTPases 在 CDH1 内吞作用和皱褶边缘形成中存在功能和物理相互作用。在过表达 Rab7 的 FRT 细胞中，观察到 Rac1 的表达和活性增加，而通过 RNAi 降低 Rab7 的表达导致 Rac1 活性降低，如 PAK1 磷酸化所测量的。我们发现，仅在 Rab7 过表达细胞中，CDH1 内吞作用显著降低，而在 Rab7 沉默细胞中不变。在 Rab7 过表达或低表达细胞中，Rab7 和 LC3B-II 共定位，并且仅在 Rab7 过表达细胞中发生大圆形结构的共定位。这些大圆形结构发生在约 10%的细胞群体中；其中一些（61%）显示 Rab7 与 cortactin 和 f-肌动蛋白的共定位，并被鉴定为圆形背侧皱褶（CDRs），其余为成熟自噬体。我们提出，Rab7 的过表达足以诱导 CDRs。此外，在 FRT 细胞中，我们发现可溶性/活性形式的 Rab7 的表达，而不是 Rab5 或 Rab8，可被 cAMP 诱导，并且 cAMP 刺激的 FRT 细胞显示 PAK1 磷酸化增加，并且不再能够内吞 CDH1。最后，我们证明 Rab7 过表达细胞能够通过胞饮作用/CDRs 比对照细胞更有效地内吞外源性甲状腺球蛋白。我们提出，由于 Rab7 表达增加而在甲状腺自主性腺瘤中描述的主要甲状腺球蛋白内吞作用，通过 CDRs 发生。J. Cell. Physiol. 231: 1695-1708, 2016。©2015 Wiley Periodicals, Inc.
