Connexin46 is retained as monomers in a trans-Golgi compartment of osteoblastic cells

被引:103
作者
Koval, M
Harley, JE
Hick, E
Steinberg, TH
机构
[1] Department of Medicine, Washington University, School of Medicine, St. Louis
[2] Department of Medicine, Washington Univ. School of Medicine, Campus Box 8051, St. Louis, MO 63110
[3] Institute for Environmental Medicine, Department of Physiology, Univ. of Pennsylvania Sch. of Med., Philadelphia, PA 19104
关键词
D O I
10.1083/jcb.137.4.847
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
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.
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页码:847 / 857
页数:11
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