Structural and Mechanistic Insights into Ras Association Domains of Phospholipase C Epsilon

Abstract

Ras proteins signal to a number of distinct pathways by interacting with diverse effectors. Studies of ras/effector interactions have focused on three classes, Raf kinases, ral guanylnucleotide-exchange factors, and phosphatidylinositol-3-kinases. Here we describe ras interactions with another effector, the recently identified phospholipase C epsilon (PLCepsilon). We solved structures of PLCepsilon RA domains (RA1 and RA2) by NMR and the structure of the RA2/ras complex by X-ray crystallography. Although the similarity between ubiquitin-like folds of RA1 and RA2 proves that they are homologs, only RA2 can bind ras. Some of the features of the RA2/ras interface are unique to PLCepsilon, while the ability to make contacts with both switch I and II regions of ras is shared only with phosphatidylinositol-3-kinase. Studies of PLCepsilon regulation suggest that, in a cellular context, the RA2 domain, in a mode specific to PLCepsilon, has a role in membrane targeting with further regulatory impact on PLC activity.

PLCε1 regulates SDF-1α–induced lymphocyte adhesion and migration to sites of inflammation

“…PLCe1 has been characterized as a direct effector of Ras (13), and recent work has shown a tumor suppressor role for this protein in Rastriggered cancers (20,21). PLCe1 was also shown to modulate adrenergic receptor-dependent cardiac contraction and to inhibit cardiac hypertrophy (22,23).…”

Multiple roles of phosphoinositide-specific phospholipase C isozymes

“…It is the largest PLC isozyme identified up to date that has two domains which are not found in other PLC isozymes. RA domains are located at the C-terminus of PLC-ε and mediates GTP-dependent interaction with Ras family small G-proteins such as Ras or Rap (189,190). CDC25 homology domain is located at the N-terminus of PLC-ε and functions as a guanine nucleotide exchange factor (GFF) for Rap1A, one of Ras family small G-proteins (191).…”

Dysfunction of phospholipase Cγ in immune disorders and cancer

“…Rac, but rather destabilizes the γSA and thereby contributes to overcome autoinhibition and facilitate activation [31]. It is possible that other cSH2-spPH interaction contacts could have a role in this context [29].…”