Regulation of a Novel Human Phospholipase C, PLCε, through Membrane Targeting by Ras

Abstract

Phosphoinositide-specific phospholipase C (PI-PLC) plays a pivotal role in regulation of intracellular signal transduction from various receptor molecules. More than 10 members of human PI-PLC isoforms have been identified and classified into three classes ␤, ␥, and ␦, which are regulated by distinct mechanisms. Here we report identification of a novel class of human PI-PLC, named PLC⑀, which is characterized by the presence of a Ras-associating domain at its C terminus and a CDC25-like domain at its N terminus. The Ras-associating domain of PLC⑀ specifically binds to the GTP-bound forms of Ha-Ras and Rap1A. The dissociation constant for HaRas is estimated to be approximately 40 nM, comparable with those of other Ras effectors. Co-expression of an activated Ha-Ras mutant with PLC⑀ induces its translocation from the cytosol to the plasma membrane. Upon stimulation with epidermal growth factor, similar translocation of ectopically expressed PLC⑀ is observed, which is inhibited by co-expression of dominant-negative Ha-Ras. Furthermore, using a liposome-based reconstitution assay, it is shown that the phosphatidylinositol 4,5-bisphosphate-hydrolyzing activity of PLC⑀ is stimulated in vitro by Ha-Ras in a GTP-dependent manner. These results indicate that Ras directly regulates phosphoinositide breakdown through membrane targeting of PLC⑀.

Phospholipase Cɛ has a crucial role in ultraviolet B-induced neutrophil-associated skin inflammation by regulating the expression of CXCL1/KC

“…The molecular mechanism of UVB-induced PLCe activation and the downstream signaling pathways from PLCe to neutrophil infiltration in the epidermis and epidermal thickening remain to be elucidated. PLCe is activated by a variety of mechanisms via multiple upstream regulators including GTPases such as Ras, Rap1, Rap2, 17,[20][21][22] and RhoA. 17,[20][21][22] Thus, further investigation of the interaction between UVB and these regulators is necessary to reveal the exact mechanism of UVB-induced PLCe activation.…”

“…PLCe is activated by a variety of mechanisms via multiple upstream regulators including GTPases such as Ras, Rap1, Rap2, 17,[20][21][22] and RhoA. 17,[20][21][22] Thus, further investigation of the interaction between UVB and these regulators is necessary to reveal the exact mechanism of UVB-induced PLCe activation. As activated PLCe produces the PKC activator, diacylglycerol, it is possible that PLCe stimulates UVB-induced epidermal neutrophil infiltration and epidermal thickening through a PKC-mediated mechanism.…”

“…17 Diacylglycerol and inositol 1,4,5-trisphosphate induce the activation of protein kinase C (PKC) and mobilization of calcium from intracellular stores, respectively. 18,19 PLCe was identified by us 19,20 and other groups 21,22 as a downstream effector of the Ras family small GTPases. It has been suggested that PLCe mediates diverse signals from outside the cell because of the multiple regulatory mechanisms of the enzyme.…”

Prognostic Value of PLCE1 Expression in Upper Gastrointestinal Cancer: a Systematic Review and Meta-analysis

“…PLCE1 functions as an effector of guanosine triphosphatases (Ras, Rap1, and Rap2), which are involved in the regulation of cell growth, differentiation, apoptosis, and angiogenesis (Song et al, 2001). Recent studies have shown that PLCE1 may serve a critical function in the carcinogenesis process of esophageal and gastric cancers (Yu et al, 2014;Zhao et al, 2014) and have identified its involvement in various cancers, such as carcinoma of bladder (Ou et al, 2010), colorectal (Wang et al, 2012b), head and neck (Bourguignon et al, 2006), and skin (Bai et al, 2004) cancers.…”

Crucial Role of Phospholipase Cε in Skin Inflammation Induced by Tumor-Promoting Phorbol Ester

“…We and others identified PLCq as an effector of Ras family small GTPases (Ras, Rap1, and Rap2), which bind directly to its Rasassociating domain (3)(4)(5)(6). Subsequent studies have shown that PLCq is also activated by small GTPase RhoA and heterotrimeric G proteins Ga12 and Gh1g2 (6).…”