Connexin46 is retained as monomers in a trans-Golgi compartment of osteoblastic cells.
Connexin46 is retained as monomers in a trans-Golgi compartment of osteoblastic cells.
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DOI：
10.1083/jcb.137.4.847
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发表时间：
1997-05-19
期刊：
影响因子：
--
通讯作者：
Steinberg TH
中科院分区：
文献类型：
--
作者：
Koval M;Harley JE;Hick E;Steinberg TH
缝隙连接蛋白是一种缝隙连接蛋白，可以形成水通道，使相邻细胞相互连接。大鼠成骨细胞表达连接蛋白43(Cx43)，在细胞表面形成功能性缝隙连接。我们发现ROS 17/2.8骨肉瘤细胞、UMR 106-01骨肉瘤细胞和原代大鼠颅骨成骨细胞也表达另一种缝隙连接蛋白Cx46。Cx46是晶状体质膜缝隙连接的主要成分。相反，成骨细胞表达的Cx46主要定位于细胞内的核周室，这似乎是免疫荧光共定位确定的TGN的一个方面。转染大鼠Cx46基因的HeLa细胞(Hela/Cx46)在细胞表面组装Cx46形成功能性缝隙连接通道。大鼠晶状体和Hela/Cx46细胞均表达53-kD(非磷酸化)和68-kD(磷酸化)Cx46，而成骨细胞仅产生53-kD。为了检测连接蛋白的组装，用1%Triton X-100溶解提取物的蔗糖梯度速度沉淀分析从低聚物中拆分单体。当Cx43组装成多聚体复合体时，ROS细胞只含有Cx46的单体形式。相反，大鼠晶状体和Hela/Cx46细胞表达的Cx46被组装成多聚体。这些研究表明，两个密切相关的连接蛋白的组装和细胞表面表达在同一细胞中受到不同的调节。此外，连接蛋白从TGN到细胞表面的运输可能需要寡聚化。
Connexins are gap junction proteins that form aqueous channels to interconnect adjacent cells. Rat osteoblasts express connexin43 (Cx43), which forms functional gap junctions at the cell surface. We have found that ROS 17/2.8 osteosarcoma cells, UMR 106-01 osteosarcoma cells, and primary rat calvarial osteoblastic cells also express another gap junction protein, Cx46. Cx46 is a major component of plasma membrane gap junctions in lens. In contrast, Cx46 expressed by osteoblastic cells was predominantly localized to an intracellular perinuclear compartment, which appeared to be an aspect of the TGN as determined by immunofluorescence colocalization. Hela cells transfected with rat Cx46 cDNA (Hela/Cx46) assembled Cx46 into functional gap junction channels at the cell surface. Both rat lens and Hela/Cx46 cells expressed 53-kD (nonphosphorylated) and 68-kD (phosphorylated) forms of Cx46; however, only the 53-kD form was produced by osteoblasts. To examine connexin assembly, monomers were resolved from oligomers by sucrose gradient velocity sedimentation analysis of 1% Triton X-100–solubilized extracts. While Cx43 was assembled into multimeric complexes, ROS cells contained only the monomer form of Cx46. In contrast, Cx46 expressed by rat lens and Hela/Cx46 cells was assembled into multimers. These studies suggest that assembly and cell surface expression of two closely related connexins were differentially regulated in the same cell. Furthermore, oligomerization may be required for connexin transport from the TGN to the cell surface.