Impaired trafficking of connexins in androgen-independent human prostate cancer cell lines and its mitigation by alpha-catenin.
Gap junctions, composed of connexins, provide a pathway of direct intercellular communication for the diffusion of small molecules between cells. Evidence suggests that connexins act as tumor suppressors. We showed previously that expression of connexin-43 and connexin-32 in an indolent prostate cancer cell line, LNCaP, resulted in gap junction formation and growth inhibition. To elucidate the role of connexins in the progression of prostate cancer from a hormone-dependent to -independent state, we introduced connexin-43 and connexin-32 into an invasive, androgen-independent cell line, PC-3. Expression of these proteins in PC-3 cells resulted in intracellular accumulation. Western blot analysis revealed a lack of Triton-insoluble, plaque-assembled connexins. In contrast to LNCaP cells, connexins could not be cell surface-biotinylated and did not reside in the cell surface derived endocytic vesicles, in PC-3 cells, suggesting impaired trafficking to the cell surface. Intracellular accumulation of connexins was observed in several androgen-independent prostate cancer cell lines. Transient expression of alpha-catenin facilitated the trafficking of both connexins to the cell surface and induced gap junction assembly. Our results suggest that impaired trafficking, and not the inability to form gap junctions, is the major cause of communication deficiency in human prostate cancer cell lines.
Govindarajan
Rajgopal
R
Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
Zhao
Sumin
S
Song
Xiao-Hong
XH
Guo
Rong-Jun
RJ
Wheelock
Margaret
M
Johnson
Keith R
KR
Mehta
Parmender P
PP
D019921:Biotinylation; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D009097:Multienzyme Complexes / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D021381:Protein Transport; D012190:Retroviridae / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D051178:alpha Catenin; D000097002:Gap Junction beta-1 Protein
D018031:Connexin 43; D017630:Connexins; D003546:Cysteine Endopeptidases; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D009097:Multienzyme Complexes; D017830:Octoxynol; D046988:Proteasome Endopeptidase Complex; D051178:alpha Catenin; D000097002:Gap Junction beta-1 Protein; C495273:CTNNA1 protein, human