Leibniz Institut für Molekulare Pharmakologie, Berlin-Buch, Germany.
Ann N Y Acad Sci. 2012 Jun;1257:29-37. doi: 10.1111/j.1749-6632.2012.06567.x.
Claudin proteins are involved in the paracellular tightening of epithelia and endothelia. Their internalization, which can be modulated by extracellular stimuli, for example, proinflammatory cytokines, is a prerequisite for the regulation of the paracellular barrier to allow, for instance, cell migration or drug delivery. The internalization of peptide sequences of claudins is completely unknown. Here, we studied the internalization of two peptides, TAMRA-claudin-1 and TAMRA-claudin-5, derivatives of the extracellular loop of claudin-1 and -5, respectively, in either epithelial or endothelial cells. The cellular uptake of the claudin-1 peptide follows the clathrin-mediated endocytosis as indicated by inhibitors and respective tracers for colocalization. In addition, macropinocytosis and caveolae-mediated endocytosis of the peptide was observed. In contrast, the claudin-5 peptide is mainly internalized via the caveolae-mediated endocytosis evidenced by the colocalization with respective tracers and vesicle markers, whereas the nonselective macropinocytosis seems to be involved in a less effective manner. In conclusion, the assumption is supported that claudin peptides can be internalized by specific and nonspecific pathways.
紧密连接蛋白参与上皮细胞和内皮细胞的细胞旁紧密连接。细胞旁屏障的调节需要紧密连接蛋白的内化，这一过程可以被细胞外刺激（例如促炎细胞因子）调节，从而允许细胞迁移或药物传递。目前，我们对紧密连接蛋白肽段的内化过程还知之甚少。本研究分别检测了 Claudin-1 和 Claudin-5 的细胞外环肽段（TAMRA-Claudin-1 和 TAMRA-Claudin-5）在上皮细胞或内皮细胞中的内化情况。 Claudin-1 肽段的细胞内摄取遵循网格蛋白介导的内吞作用，这可通过抑制剂和相应的共定位示踪剂来证实。此外，还观察到该肽段的巨胞饮作用和小窝蛋白介导的内吞作用。相反， Claudin-5 肽段主要通过小窝蛋白介导的内吞作用内化，这可通过与相应示踪剂和囊泡标记物的共定位来证明，而非选择性的巨胞饮作用似乎以较低效率参与其中。总之，本研究支持这样的假设，即紧密连接肽段可以通过特异性和非特异性途径被内化。
