Ultrastructural analysis of the organization and distribution of insulin receptors on the surface of 3T3‐L1 adipocytes: Rapid microaggregation and migration of occupied receptors
Ultrastructural analysis of the organization and distribution of insulin receptors on the surface of 3T3‐L1 adipocytes: Rapid microaggregation and migration of occupied receptors
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DOI：
10.1002/jcp.1041230204
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发表时间：
1985-05
影响因子：
5.6
通讯作者：
Robert M. Smith;M. Cobb;O. Rosen;L. Jarett
中科院分区：
文献类型：
--
作者：
Robert M. Smith;M. Cobb;O. Rosen;L. Jarett
使用单体铁蛋白-胰岛素和高分辨率电子显微镜分析来研究分化的 3T3-L1 脂肪细胞上胰岛素受体的组织、分布和运动。对前缀细胞结合的分析表明，胰岛素最初占据优先位于微绒毛上的单个和成对受体。大多数受体 (60%) 被发现为单分子，30% 为成对分子。在37%C下1分钟内，未固定细胞上50%的受体出现在绒毛间质膜上，并且超过70%的总受体已微聚集。到 30 分钟时，微绒毛上只有 7% 的受体是单个或配对的分子。大多数受体位于绒毛间膜上，其中 95% 的受体成组。绒毛间质膜上的受体基团可以在无涂层内陷和有涂层凹坑中找到。非包被内陷和包被凹坑中占据的受体浓度相似；然而，未包被的凹陷所含胰岛素受体的数量是包被的凹陷的十倍。本研究中的观察结果与使用相同技术对大鼠脂肪细胞报告的结果形成对比（Jarett 和 Smith，1977）。脂肪细胞上的胰岛素受体最初被分组并随机分布在整个细胞表面，并且没有微聚集成更大的组。大鼠脂肪细胞上的胰岛素受体在非涂层凹陷中被发现，但被排除在涂层凹坑之外。大鼠和 3T3-L1 脂肪细胞之间胰岛素受体的组织和行为的差异表明，调节胰岛素受体的初始组织和占据的受体聚集的机制可能是由组织特异性过程控制的。由于这两种细胞类型对胰岛素同样敏感，因此细胞表面胰岛素受体的初始组织和分布的差异可能与这些细胞对胰岛素的敏感性或生物反应性无关，但可能影响其他过程，例如受体调节和内化。另一方面，两种细胞类型上占据的受体的微聚集体可能与生物反应性有关。
Monomeric ferritin‐insulin and high‐resolution electron microscopic analysis were used to study the organization, distribution, and movement of insulin receptors on differentiated 3T3‐L1 adipocytes. Analysis of the binding to prefixed cells showed that insulin initially occupied single and paired receptors preferentially located on microvilli. The majority of receptors (60%) were found as single molecules and 30% were pairs. In 1 min at 37%C, 50% of the receptors on nonfixed cells were found on the intervillous plasma membrane and more than 70% of the total receptors had microaggregated. By 30 min only 7% of the receptors were single or paired molecules on microvilli. The majority were on the intervillous membrane, with 95% of those receptors in groups. The receptor groups on the intervillous plasma membrane could be found in both noncoated invaginations and coated pits. The concentration of occupied receptors in the noncoated invaginations and the coated pits was similar; however, ten times more noncoated invaginations than coated pits contained occupied insulin receptors. The observations in this study contrast with those reported on rat adipocytes using identical techniques (Jarett and Smith, 1977). Insulin receptors on adipocytes were initially grouped and randomly distributed over the entire cell surface and did not microaggregate into larger groups. Insulin receptors on rat adipocytes were found in non‐coated invaginations but were excluded from the coated pits. The differences in the organization and behavior of the insulin receptor between rat and 3T3‐L1 adipocytes suggest that the mechanisms regulating the initial organization of insulin receptors and the aggregation of occupied receptors may be controlled by tissue‐specific processes. Since both of these cell types are equally insulin sensitive, the differences in the initial organization and distribution of the insulin receptors on the cell surface may not be related to the sensitivity or biological responsiveness of these cells to insulin but may affect other processes such as receptor regulation and internalization. On the other hand, the microaggregates of occupied receptors on both cell types may relate to biological responsiveness.