Inhibition of anchorage-independent cell growth, adhesion, and cyclin D1 gene expression by a dominant negative mutant of a tyrosine phosphatase.
PTP-S4/TC48 protein tyrosine phosphatase is localized in the nuclear and cytoplasmic membranes. To investigate the role of PTP-S4 in cell growth, adhesion, and transformation, normal and a catalytically inactive mutant form of this phosphatase were expressed in polyoma virus-transformed F111 fibroblast cell line, PyF. Expression of mutant PTP-S4 in PyF cells resulted in strong inhibition of anchorage-independent growth in soft agar but had no significant effect on growth in liquid culture. Tumor formation in nude mice was also reduced by mutant PTP-S4. Expression of normal PTP-S4 in PyF cells significantly increased anchorage-independent cell growth and tumor formation in nude mice. Overexpression of catalytically inactive mutant of PTP-S2/TC45 (a splice variant of PTP-S4 that is nuclear) did not inhibit anchorage-independent growth of PyF cells. Mutant PTP-S4-expressing cells were inhibited in adhesion and spreading on tissue culture plates compared to control cells. Expression of mutant PTP-S4 in PyF cells reduced the levels of cyclin D1 and cyclin A mRNA, whereas cyclin D2 mRNA level was not affected significantly. Expression of antisense cyclin D1 strongly inhibited anchorage-independent growth. Inhibition of anchorage-independent growth by mutant PTP-S4 was overcome to a large extent by coexpression of cyclin D1. These results suggest that mutant PTP-S4 inhibits anchorage-independent growth and adhesion of polyoma virus-transformed cells by interfering with the normal function of PTP-S4 upstream of cyclin D1 gene expression.
Mitra
S K
SK
Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India.
Swarup
G
G
D000818:Animals; D001943:Breast Neoplasms; D019556:COS Cells; D002448:Cell Adhesion / Q000502:physiology; D018929:Cell Culture Techniques / Q000379:methods; D002455:Cell Division / Q000502:physiology; D002522:Chlorocebus aethiops; D003470:Culture Media; D019925:Cyclin A / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics* / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D016296:Mutagenesis; D009374:Neoplasms, Experimental / Q000201:enzymology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured
D003470:Culture Media; D019925:Cyclin A; D019938:Cyclin D1; D017027:Protein Tyrosine Phosphatases