Jones J C, Kurpakus M A, Cooper H M, Quaranta V
Cell, Molecular, and Structural Biology Department, Northwestern University Medical School, Chicago, Illinois 60611.
Cell Regul. 1991 Jun;2(6):427-38. doi: 10.1091/mbc.2.6.427.
Many epithelial cells appear to use cell-substratum adhesion complexes known as hemidesmosomes as the main means of anchorage to the connective tissue. Initially recognized as distinctive electron-dense images, hemidesmosomes are still poorly understood at the biochemical level. The regulation and mode of their assembly, which is disrupted in certain blistering diseases and is critical to proper wound repair, also remains to be elucidated. The integrin alpha 6 beta 4 is expressed along the basal surface of various epithelial cells. We show here that this integrin localizes to hemidesmosomes as determined by immunoelectron microscopy using antibodies directed against both the extra- and intracytoplasmic domains of alpha 6 beta 4. This result, which agrees with a recent study, suggests a functional role for the alpha 6 beta 4 integrin in the hemidesmosomes. We therefore investigated such a potential role for this integrin using the cultured rat bladder carcinoma cell line 804G, which has the uncommon ability to form hemidesmosomes in vitro when maintained on uncoated glass substrates. By immunoprecipitation and immunofluorescence, we show that 804G cells express alpha 6 beta 4 along their basal surface in a punctate pattern that overlaps with the distribution of hemidesmosomal plaque antigens. However, this pattern is altered when cells are plated in the presence of an antiserum directed against alpha 6 beta 4. Furthermore, no hemidesmosomes are detectable at the ultrastructural level in the alpha 6 beta 4 antibody-treated cells compared with control cells. These results indicate that integrins may play a critical role in assembly and adhesive functions of the hemidesmosome.
许多上皮细胞似乎利用被称为半桥粒的细胞-基质黏附复合体作为与结缔组织锚定的主要方式。半桥粒最初被识别为独特的电子致密图像，在生化水平上仍未被充分理解。其组装的调控和模式在某些水疱性疾病中会被破坏，且对伤口的正常修复至关重要，目前仍有待阐明。整合素α6β4在各种上皮细胞的基底表面表达。我们在此表明，通过使用针对α6β4胞外和胞质内结构域的抗体进行免疫电子显微镜检测，这种整合素定位于半桥粒。这一结果与最近的一项研究一致，表明α6β4整合素在半桥粒中具有功能作用。因此，我们使用培养的大鼠膀胱癌细胞系804G来研究这种整合素的潜在作用，该细胞系在未包被的玻璃基质上培养时具有在体外形成半桥粒的罕见能力。通过免疫沉淀和免疫荧光，我们表明804G细胞沿其基底表面以点状模式表达α6β4，该模式与半桥粒斑块抗原的分布重叠。然而，当细胞在存在针对α6β4的抗血清的情况下接种时，这种模式会改变。此外，与对照细胞相比，在α6β4抗体处理的细胞中，在超微结构水平上未检测到半桥粒。这些结果表明整合素可能在半桥粒的组装和黏附功能中起关键作用。
