Jones P H, Bishop L A, Watt F M
Keratinocyte Laboratory, Imperial Cancer Research Fund, London.
Cell Adhes Commun. 1996 Nov;4(4-5):297-305. doi: 10.3109/15419069609010773.
CD9 is a member of the tetraspan (TM4) family of proteins and is abundantly expressed in the epidermis. As CD9 forms complexes with beta 1 integrins and the integrins are known to regulate keratinocyte behaviour, we investigated CD9 expression and function in human epidermal keratinocytes. CD9 was present in all the living layers of the epidermis, whereas the beta 1 integrins were largely confined to the basal layer; the same relative distribution was found in stratified cultures of keratinocytes. There was extensive co-localisation of CD9 and beta 1 integrins on microvilli and at cell-cell borders of basal keratinocytes; however, in contrast to the integrins, CD9 was not found in focal adhesions. CD9 was detected in beta 1 integrin immunoprecipitates and also in immunoprecipitates of CD44 and syndecan, but not of cadherins. CD9 was associated with alpha 3 beta 1 but not alpha 5 beta 1; small amounts of CD9 also co-immunoprecipitated with antibodies to alpha 2 beta 1 and alpha 6 beta 4. Antibodies to CD9 did not affect the proportion of keratinocytes that adhered to laminin 1, type IV collagen and fibronectin, but did inhibit motility of keratinocytes on tissue culture plastic. Like antibodies to the beta 1 integrin subunit, anti-CD9 inhibited suspension-induced terminal differentiation. These results suggest that CD9 may play a role in regulating keartinocyte motility and differentiation.
CD9是四跨膜蛋白（TM4）家族的成员，在表皮中大量表达。由于CD9与β1整合素形成复合物，且已知整合素可调节角质形成细胞的行为，因此我们研究了CD9在人表皮角质形成细胞中的表达和功能。CD9存在于表皮的所有活层中，而β1整合素主要局限于基底层；在角质形成细胞的分层培养物中也发现了相同的相对分布。在微绒毛上以及基底角质形成细胞的细胞 - 细胞边界处，CD9和β1整合素存在广泛的共定位；然而，与整合素不同的是，在粘着斑中未发现CD9。在β1整合素免疫沉淀产物中检测到了CD9，在CD44和syndecan的免疫沉淀产物中也检测到了CD9，但在钙粘蛋白的免疫沉淀产物中未检测到。CD9与α3β1相关，但与α5β1无关；少量的CD9也与抗α2β1和α6β4的抗体共免疫沉淀。抗CD9抗体不影响粘附于层粘连蛋白1、IV型胶原和纤连蛋白的角质形成细胞的比例，但确实抑制了角质形成细胞在组织培养塑料上的运动。与抗β1整合素亚基的抗体一样，抗CD9抑制悬浮诱导的终末分化。这些结果表明，CD9可能在调节角质形成细胞的运动和分化中发挥作用。
