Control of intracellular localization and function of Cx43 by SEMA3F.
Connexin genes are considered to form a family of tumor-suppressor genes. However, the mechanism of connexin-mediated growth control is not well understood. We now provide several lines of evidence which suggest that SEMA3F, a member of the class 3 semaphorin family, which is also reported to be a tumor suppressor, controls the intracellular localization and function of connexin 43 (Cx43). We employed a series of rat liver epithelial cell lines, among which we previously found that the level of expression of malignant phenotypes (IAR20 < IAR27E < IAR6-1 < IAR27F) is inversely related to that of gap junctional intercellular communication (GJIC). When we immunostained SEMA3F and Cx43 in these cell lines, the extent of immunostaining in the plasma membrane of both proteins decreased in the order of IAR20 > IAR27E > IAR6-1 > IAR27F, suggesting a close relationship between Cx43 and SEMA3F. Further studies revealed a partial colocalization of SEMA3F and Cx43 in the plasma membrane of IAR20 cells. We also found that both SEMA3F and Cx43 moved from the cytoplasm to the plasma membrane in a mouse papilloma cell line when E-cadherin became functional after transferring the cells from low- to high-calcium conditions. When SEMA3F gene expression was inhibited by siRNA in IAR20 cells, Cx43 localization in the plasma membrane and GJIC ability were reduced. Moreover, we found that SEMA3F binds with the cytoplasmic loop domain of Cx43, employing the yeast two-hybrid complementation and screening assays. Taken together, these results strongly suggest that SEMA3F directly associates with Cx43 and controls its intracellular localization and function.
Kawasaki
Yumi
Y
Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1-2, Gakuen, Sanda, Hyogo, Japan.
Kubomoto
Aya
A
Yamasaki
Hiroshi
H
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D017629:Gap Junctions / Q000502:physiology; D006321:Heart / Q000502:physiology; D022781:Hepatocytes / Q000378:metabolism; D007365:Intercellular Junctions / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D020798:Two-Hybrid System Techniques
D018031:Connexin 43; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; C506913:Sema3F protein, rat; D002118:Calcium