Scott Glynis, Leopardi Sonya, Printup Stacey, Madden Brian C
Department of Dermatology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
J Cell Sci. 2002 Apr 1;115(Pt 7):1441-51. doi: 10.1242/jcs.115.7.1441.
Melanosomes are specialized melanin-synthesizing organelles critical for photoprotection in the skin. Melanosome transfer to keratinocytes, which involves whole organelle donation to another cell, is a unique biological process and is poorly understood. Time-lapse digital movies and electron microscopy show that filopodia from melanocyte dendrites serve as conduits for melanosome transfer to keratinocytes. Cdc42, a small GTP-binding protein, is known to mediate filopodia formation. Melanosome-enriched fractions isolated from human melanocytes expressed the Cdc42 effector proteins PAK1 and N-WASP by western blotting. Expression of constitutively active Cdc42 (Cdc42(V12)) in melanocytes co-cultured with keratinocytes induced a highly dendritic phenotype with extensive contacts between melanocytes and keratinocytes through filopodia, many of which contained melanosomes. These results suggest a unique role for filopodia in organelle transport and, in combination with our previous work showing the presence of SNARE proteins and rab3a on melanosomes, suggest a novel model system for melanosome transfer to keratinocytes.
黑素小体是专门用于合成黑色素的细胞器，对皮肤的光保护至关重要。黑素小体向角质形成细胞的转移，这涉及到将整个细胞器捐赠给另一个细胞，是一个独特的生物学过程，目前了解甚少。延时数字电影和电子显微镜显示，黑素细胞树突的丝状伪足充当黑素小体转移到角质形成细胞的通道。已知小GTP结合蛋白Cdc42介导丝状伪足的形成。通过蛋白质免疫印迹法，从人黑素细胞中分离出的富含黑素小体的组分表达了Cdc42效应蛋白PAK1和N-WASP。在与角质形成细胞共培养的黑素细胞中，组成型活性Cdc42（Cdc42(V12)）的表达诱导了高度树突状的表型，黑素细胞和角质形成细胞之间通过丝状伪足广泛接触，其中许多丝状伪足含有黑素小体。这些结果表明丝状伪足在细胞器运输中具有独特作用，并且结合我们之前关于黑素小体上存在SNARE蛋白和rab3a的研究工作，提示了一个黑素小体转移到角质形成细胞的新模型系统。
