Roach M C, Boucher V L, Walss C, Ravdin P M, Ludueña R F
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760, USA.
Cell Motil Cytoskeleton. 1998;39(4):273-85. doi: 10.1002/(SICI)1097-0169(1998)39:4<273::AID-CM3>3.0.CO;2-4.
Tubulin, the subunit protein of microtubules, is an alpha/beta heterodimer. In many organisms, both alpha and beta consist of various isotypes. Although the isotypes differ in their tissue distributions, the question of whether the isotypes perform different functions in vivo is unanswered. In mammals, the betaI and betaIV isotypes are quite widespread, and betaII is less so, while betaIII and betaVI have narrow distributions and betaV distribution is unknown. As a tool for localizing the isotypes, we report the preparation of a monoclonal antibody specific for betaI, to add to our previously described monoclonal antibodies specific for betaII, betaIII, and betaIV [Banerjee et al., J. Biol. Chem. 263:3029-3034, 1988; 265:1794-1799, 1990; 267:5625-5630, 1992]. In order to prepare this antibody, we have purified betaI-rich rat thymus tubulin. We have used our battery of antibodies to localize the beta isotypes in four human tissues: oviduct, skin, colon, and pancreas. We have found striking differences in their tissue distributions. There is little or no betaIII in these tissues, except for the columnar epithelial cells of the colon. BetaII is restricted to very few cells, except in the skin, where it is concentrated in the stratum granulosum. BetaI is widespread in all the epithelia. In the skin it is found in the entire stratum malpighii. In the oviduct, betaI is found largely in the nonciliated epithelial cells. In the exocrine pancreas, betaI occurs only in the centroacinar cells and not in the acinar cells; the latter do not stain with any of these antibodies. BetaIV is present at very low levels in skin and pancreas. By contrast, it is prominent in the colon and also in the oviduct, where it occurs in all the epithelial cells, especially in the ciliated cells, with the highest concentrations in the cilia themselves. These results suggest that the regulation of the expression and localization of isotypes in tissues is very complex.
微管蛋白是微管的亚基蛋白，是一种α/β异二聚体。在许多生物体中，α和β都由多种同种型组成。尽管这些同种型在组织分布上有所不同，但它们在体内是否执行不同功能的问题仍未得到解答。在哺乳动物中，βI和βIV同种型分布相当广泛，βII则较少，而βIII和βVI分布狭窄，βV的分布情况未知。作为定位这些同种型的工具，我们报告了一种针对βI的单克隆抗体的制备，以补充我们先前描述的针对βII、βIII和βIV的单克隆抗体[Banerjee等人，《生物化学杂志》263:3029 - 3034，1988；265:1794 - 1799，1990；267:5625 - 5630，1992]。为了制备这种抗体，我们纯化了富含βI的大鼠胸腺微管蛋白。我们使用一系列抗体在四种人体组织（输卵管、皮肤、结肠和胰腺）中定位β同种型。我们发现它们在组织分布上存在显著差异。除结肠的柱状上皮细胞外，这些组织中几乎没有或不存在βIII。βII仅限于极少数细胞，除了在皮肤中，它集中在颗粒层。βI在所有上皮中广泛分布。在皮肤中，它存在于整个马尔皮基层。在输卵管中，βI主要存在于非纤毛上皮细胞中。在外分泌胰腺中，βI仅存在于中央腺泡细胞中，而腺泡细胞中不存在；后者不会被这些抗体中的任何一种染色。βIV在皮肤和胰腺中的含量非常低。相比之下，它在结肠中很突出，在输卵管中也很突出，在输卵管中它存在于所有上皮细胞中，尤其是在纤毛细胞中，在纤毛本身中的浓度最高。这些结果表明，组织中同种型表达和定位的调控非常复杂。
