Overexpression of myosin VI in prostate cancer cells enhances PSA and VEGF secretion, but has no effect on endocytosis.
Tissue expression microarrays, employed to determine the players and mechanisms leading to prostate cancer development, have consistently shown that myosin VI, a unique actin-based motor, is upregulated in medium-grade human prostate cancers. Thus, to understand the role of myosin VI in prostate cancer development, we have characterized its intracellular localization and function in the prostate cancer cell line LNCaP. Using light and electron microscopy, we identified myosin VI on Rab5-positive early endosomes, as well as on recycling endosomes and the trans-Golgi network. Intracellular targeting seems to involve two myosin VI-interacting proteins, GIPC and LMTK2, both of which can be co-immunoprecipitated with myosin VI from LNCaP cells. The absence of Disabled-2 (Dab2), a tumour suppressor and myosin VI-binding partner, inhibits recruitment of myosin VI to endocytic structures at the plasma membrane in LNCaP cells, but interestingly has no effect on endocytosis. Small interfering RNA-mediated downregulation of myosin VI expression results in a significant reduction in prostate-specific antigen (PSA) and vascular endothelial growth factor (VEGF) secretion in LNCaP cells. Our results suggest that in prostate cancer cells, myosin VI regulates protein secretion, but the overexpression of myosin VI has no major impact on clathrin-mediated endocytosis.
Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge, UK.
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C
Puri
M V
MV
Chibalina
S D
SD
Arden
A J
AJ
Kruppa
J
J
Kendrick-Jones
F
F
Buss
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D015870:Gene Expression; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D017430:Prostate-Specific Antigen / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; C102885:DAB2 protein, human; C492009:GIPC1 protein, human; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; C089785:myosin VI; D049452:Green Fluorescent Proteins; C470798:LMTK2 protein, human; D017346:Protein Serine-Threonine Kinases; D017430:Prostate-Specific Antigen; D018995:Myosin Heavy Chains