Mechanism of Translocation of Microvilli Accompanying Cap Formation of Surface Receptors

[摘要] References(33)Surface architecture of lymphocytes undergoing ligandindependent (LI-) cap formation in hypertonic medium was studied by scanning electron microscopy (SEM). When lymphocytes were incubated in hypertonic medium, surface microvilli* on the cell surface were first replaced by lamellae* prior to the translocation of these structures. Microvilli were accumulated in the region of the cap as surface receptors moved to form a cap in one pole of the cell. The surface of cells with a cap and accumulated microvilli was covered with lamellae until LI-cap formation was fully induced. Cells with accumulated microvilli at one pole and with smooth surface on the residual cell body appeared subsequently after incubation in a hypertonic medium for 15 min or longer. The shape of the stumps of projections on the cell surface of lymphocytes was examined by freeze-fracture methods, which verified the observations made by SEM.These results led to the hypothesis that the accumulation of microvilli at one pole of the cell during LI-cap formation occurs by transformation of microvilli into lamellae, the translocation of this latter structure to one pole and the reverse transformation of lamellae into microvilli.Since both microvilli and lamellae are known to be composed of microfilamentous structures, redistribution of these structures that accompany LI-cap formation are probably associated with the redistribution of actin, the main structural protein of the microfilaments. This was shown to be the case by indirect immunofluorescence methods using actin antibody.

[学科分类] 分子生物学，细胞生物学和基因