Signaling properties and expression in normal and tumor tissues of two phospholipase C epsilon splice variants.
Phospholipase Cepsilon (PLCepsilon) is a novel member of phosphoinositide-specific phospholipase C enzymes with a unique regulatory link to Ras GTP-ases. In the present studies, we establish existence of two splice variants (PLCepsilon1a and PLCepsilon1b) derived from human PLCepsilon1 gene. When expressed in COS or HEK293 cells, PLCepsilon1a and PLCepsilon1b have similar potential to be stimulated by diverse signaling pathways via tyrosine kinase and G-protein coupled receptors and share the ability to function as an effector of Ras. The expression pattern shows broader mRNA expression of PLCepsilon1a in normal tissues; furthermore, in most cell lines expressing PLCepsilon, PLCepsilon1a is the only splice variant present. Analysis of normal/tumor matched pairs derived from colon and rectum demonstrates greatly reduced expression levels in tumor tissues. Further studies in a colorectal tumor cell line lacking PLCepsilon show restoration of transcription of PLCepsilon1a and PLCepsilon1b by demethylating agent 5-aza-2'-deoxycytidine, suggesting epigenetic silencing through hypermethylation. In addition, expression of exogenous PLCepsilon in this cell line demonstrates inhibitory effects of PLCepsilon on cell viability and proliferation. Taken together, our findings suggest that regulatory mechanisms controlling expression of PLCepsilon, broadened by diversity introduced by splice variants, could play important role in PLCepsilon regulation in normal and tumor cells.
Sorli
Sonia Caroline
SC
Cancer Research UK Centre for Cell and Molecular Biology, Chester Beatty Laboratories, The Institute of Cancer Research, Fulham Road, London SW3 6JB, UK.
Bunney
Tom D
TD
Sugden
Peter H
PH
Paterson
Hugh F
HF
Katan
Matilda
M
D017398:Alternative Splicing / Q000235:genetics* / Q000502:physiology; D015179:Colorectal Neoplasms / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D054801:Phosphoinositide Phospholipase C; D015398:Signal Transduction / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000235:genetics* / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; C423320:phospholipase C epsilon; D018631:ras Proteins