Intracellular trafficking of tyrosine kinases and their differential functions

SRC家族酪氨酸激酶是胞浆酶，其N端的脂质修饰导致其定位于内膜和质膜。在这项研究中，我们研究了Src家族酪氨酸激酶及其负调控因子Chk酪氨酸激酶的细胞内转运、定位和功能。我们的研究结果描述如下。H_2O_2刺激细胞可诱导高尔基体上LYN对Annexin 11的酪氨酸磷酸化，导致Annexin 11从高尔基体转位到内质网。LYN激活区是LYN运输的重要组成部分，它与两种蛋白质结合在一起，这两种蛋白质是通过质谱仪鉴定的。Chk的核定位导致细胞核动态多分叶，延长细胞周期的S期。Chk的N-末端结构域与核和核基质结合，Chk诱导的核酪氨酸磷酸化有助于抑制细胞增殖。与Lyn、c-Yes和Fyn不同的是，c-Src通过其N-末端与大胞质小体结合，从它们在膜褶皱发生时开始，一直到它们向心运输，直到与晚期的内小体和溶酶体融合。C-Src从细胞膜和胞内细胞器迅速被募集到巨噬细胞体膜上。SRC信号调节HeLa细胞胞质分裂的最后一步，称为脱落。脱落的完成需要在有丝分裂的早期阶段(分裂沟形成之前)由Src介导的酪氨酸磷酸化，随后通过Rab11驱动的囊泡运输将其输送到中体。有丝分裂早期的SRC激酶活性介导了胞质分裂晚期ERK的激活。激活的ERK被Src激酶下游的MEK磷酸化，募集到中体在完成脱落过程中起着重要作用。

Src-family tyrosine kinases are cytosolic enzymes, and lipid modification at their N-termini leads to their localization to endomembranes as well as the plasma membrane. In this study, we examined intracellular trafficking, localization and function of Src-family tyrosine kinases and their negative regulator Chk tyrosine kinase. Our findings are described as follows.1. Stimulation of cells with H_2O_2 induces tyrosine phosphorylation of annexin 11 by Lyn that is present on the Golgi apparatus, leading to the translocation of annexin 11 from the Golgi to the endoplasmic reticulum.2. Lyn kinase domain, which is important for Lyn trafficking, associates with two proteins that are identified by mass spectrometry.3. Nuclear localization of Chk induces dynamic multi-lobulation of the nucleus and prolonged S phase of the cell cycle. The N-terminal domain of Chk associates with the nucleus and the nuclear matrix, and nuclear tyrosine phosphorylation induced by Chk contributes to inhibition of cell proliferation.4. c-Src, unlike Lyn, c-Yes and Fyn, associates with macropinosomes via its N-terminus continuously from their generation at membrane ruffles, through their centripetal trafficking, to fusion with late endosomes and lysosomes. c-Src is rapidly recruited to macropinosomal membranes from the plasma membrane and intracellular organelles.5. Src signaling regulates the terminal step in cytokinesis called abscission in HeLa cells. Completion of abscission requires Src-mediated tyrosine phosphorylation during early stages of mitosis (before cleavage furrow formation), which is subsequently delivered to the midbody through Rab11-driven vesicle transport. Src kinase activity during the early mitosis mediates ERK activation in late cytokinesis. Recruitment of activated ERK, which is phosphorylated by MEK downstream of Src kinases, to the midbody plays an important role in completion of abscission.