Signaling properties and expression in normal and tumor tissues of two phospholipase C epsilon splice variants

Abstract

Phospholipase Ce (PLCe) 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 (PLCe1a and PLCe1b) derived from human PLCe1 gene. When expressed in COS or HEK293 cells, PLCe1a and PLCe1b 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 PLCe1a in normal tissues; furthermore, in most cell lines expressing PLCe, PLCe1a 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 PLCe show restoration of transcription of PLCe1a and PLCe1b by demethylating agent 5-aza-2 0 -deoxycytidine, suggesting epigenetic silencing through hypermethylation. In addition, expression of exogenous PLCe in this cell line demonstrates inhibitory effects of PLCe on cell viability and proliferation. Taken together, our findings suggest that regulatory mechanisms controlling expression of PLCe, broadened by diversity introduced by splice variants, could play important role in PLCe regulation in normal and tumor cells.

Multiple roles of phosphoinositide-specific phospholipase C isozymes

“…But there are a number of genes that use alternative splicing to generate several numbers of isoforms. Alternative splicing variants have been previously reported for several of PLC isozymes including rat PLC-β1 (39), human PLC-β2 (40), rat PLC-β4 (41), rat PLC-δ4 (33), and human PLC-ε (42). Here, we analyzed and identified additional splicing variants for PLC isozyme using BLAST server in mouse species.…”

“…Two splicing variants of human PLC-ε with a different N-terminal region have been reported (42), but mouse PLC-ε isozyme was found to have two novel splicing variants in a different region. Surprisingly, mouse PLC-ε1c lacks the Ras-GEF domain and partial PH domain at the N-terminus.…”

Phosphoinositide-specific phospholipase C in health and disease

“…Alternative splicing variants have been reported for several of PI-PLC isozymes, including human and rat PI-PLC ␤ 1, human PI-PLC ␤ 2, rat PI-PLC ␤ 4, rat PI-PLC ␦ 4, and human PI-PLC (47)(48)(49)(50)(51)(52).…”

“…Three splicing variants of the human PI-PLC 1 gene have been reported, with the second variant showing a different N-terminal region, and the third variant using an alternate in-frame splice site in the coding region that results in a shorter protein ( 52 ).…”

Phospholipase C ε‑1 gene polymorphisms and prognosis of esophageal cancer patients from a high‑incidence region in northern China

“…Hence, PLCE1 plays a crucial role in regulating cell growth, differentiation, apoptosis and angiogenesis (15). It was previously demonstrated that PLCE1 was involved in the development and progression of various cancers, including esophageal cancer (3,10,(16)(17)(18)(19)(20)(21)(22). In addition, the expression of PLCE1 was associated with the survival of patients with esophageal cancer (23,24).…”