Phosphorylation of the discs large tumour suppressor protein controls its membrane localisation and enhances its susceptibility to HPV E6-induced degradation.
The Discs Large (Dlg) protein is intimately involved in regulating cell polarity and cell proliferation, and is targeted by the high-risk Human Papillomavirus (HPV) E6 proteins for proteasome-mediated degradation. We show here that exposure of cells to osmotic shock induces the hyperphosphorylation of Dlg and its concomitant accumulation within the cell membrane at sites of cell contact, a process that requires an intact actin filament network. In addition, hyperphosphorylation of Dlg also renders it more susceptible to degradation induced by the HPV-18 E6 oncoprotein. Mutational analysis of Dlg identifies a region within the first 185 amino acids as being important for this, with phosphorylation on residue S158 being responsible for its enhanced targeting by the E6 oncoprotein. Using specific kinase inhibitors, we show that Jun N-terminal kinase (JNK) is in part responsible for this phosphorylation, and for the subsequent Dlg accumulation at sites of cell contact. These results further support the notion of a complex phosphorylation-dependent regulation of Dlg, both with respect to its precise cellular localisation and to its susceptibility to proteasome-mediated degradation.
International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
P
P
Massimi
N
N
Narayan
A
A
Cuenda
L
L
Banks
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism* / Q000821:virology; D000074288:Discs Large Homolog 1 Protein; D052162:Human papillomavirus 16 / Q000502:physiology*; D052161:Human papillomavirus 18 / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D009856:Oncogene Proteins, Viral / Q000502:physiology*; D009997:Osmotic Pressure; D010766:Phosphorylation; D012097:Repressor Proteins / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism* / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; C068651:E6 protein, Human papillomavirus type 16; D008565:Membrane Proteins; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D025521:Tumor Suppressor Proteins