Involvement of protein kinase Cδ in contact-dependent inhibition of growth in human and murine fibroblasts

Abstract

There is evidence that protein kinase C d (PKCd) is a tumor suppressor, although its physiological role has not been elucidated so far. Since important anti-proliferative signals are mediated by cell ± cell contacts we studied whether PKCd is involved in contact-dependent inhibition of growth in human (FH109) and murine (NIH3T3) ®broblasts. Cell ± cell contacts were imitated by the addition of glutardialdehyde-®xed cells to sparsely seeded ®broblasts. Downregulation of the PKC isoforms a, d, e, and m after prolonged treatment with 12-Otetradecanoylphorbol-13-acetate (TPA, 0.1 mM) resulted in a signi®cant release from contact-inhibition in FH109 cells. Bryostatin 1 selectively prevented TPA-induced PKCd-downregulation and reversed TPA-induced release from contact-inhibition arguing for a role of PKCd in contact-inhibition. In accordance, the PKCd speci®c inhibitor Rottlerin (1 mM) totally abolished contactinhibition. Interestingly, immuno¯uorescence revealed a rapid translocation of PKCd to the nucleus when cultures reached con¯uence with a peak in early-mid G1 phase. Nuclear translocation of PKCd in response to cell ± cell contacts could also be demonstrated after subcellular fractionation by Western blotting and by measuring PKCd-activity after immunoprecipitation. Transient transfection of NIH3T3 cells with a dominant negative mutant of PKCd induced a transformed phenotype. We conclude that PKCd is involved in contact-dependent inhibition of growth. Oncogene (2001) 20, 5143 ± 5154.

Counter Regulatory Effects of PKC βII and PKC δ on Coronary Endothelial Permeability

“…The distribution of PKC␦ at cell-cell contacts remained low, without significant colocalization with VE-cadherin. While the intracellular localization and nuclear translocation of the novel PKCs have been observed in other cell types, 36,37 this study provides evidence for prominent distribution of PKC␦ in the cytoplasm with minimal junctional association in the coronary vascular endothelium. The primary intracellular location of this isoform may contribute to its barrier protective function in that it enables close interactions with cytoskeletal elements that stabilize the contractile machinery and maintain cell-cell adhesions.…”

TCDD deregulates contact inhibition in rat liver oval cells via Ah receptor, JunD and cyclin A

“…Western blot analysis was performed as described (Heit et al, 2001;Faust et al, 2005). Quantification of western blot signals was performed using NIH Image (version 1.61).…”

“…In contrast, transformed cells are characterized by loss of contact inhibition manifested by a higher saturation density and the emergence of multi-layered foci. Despite its importance for cell cycle control, knowledge about the molecular mechanisms mediating contact inhibition and its deregulation during tumourigenesis is still scarce (Dietrich et al, 1997;Wieser et al, 1999;Heit et al, 2001;Faust et al, 2005).…”

The Hippo-YAP signaling pathway and contact inhibition of growth

“…Many different signaling pathways have been implicated in the contact inhibition of growth, and a number of pathways seem to be altered as a function of cell density (Polyak et al, 1994;Wieser et al, 1999;Heit et al, 2001;Faust et al, 2005;Li et al, 2012;McClatchey and Yap, 2012). However, the Hippo pathway has been found to have an important role in contact inhibition and growth regulation through physical properties of cells.…”