Dual role of cAMP and involvement of both G-proteins and ras in regulation of ERK2 in Dictyostelium discoideum.

Abstract

Dictyostelium discoideum expresses two Extracellular signal Regulated Kinases, ERK1 and ERK2, which are involved in growth, multicellular development and regulation of adenylyl cyclase. Binding of extracellular cAMP to cAMP receptor 1, a G‐protein coupled cell surface receptor, transiently stimulates phosphorylation, activation and nuclear translocation of ERK2. Activation of ERK2 by cAMP is dependent on heterotrimeric G‐proteins, since activation of ERK2 is absent in cells lacking the Galpha4 subunit. The small G‐protein rasD also activates ERK2. In cells overexpressing a mutated, constitutively active rasD, ERK2 activity is elevated prior to cAMP stimulation. Intracellular cAMP and cAMP‐dependent protein kinase (PKA) are essential for adaptation of the ERK2 response. This report shows that multiple signalling pathways are involved in regulation of ERK2 activity in D.discoideum.

Lysophosphatidic Acid- and Gβ-Dependent Activation of Dictyostelium MAP Kinase ERK2

“…Each stimulation was stopped by lyzing the cells in ice-cold buffer A (final concentrations 20 mM Tris pH 8.0, 6.7 mM KCl, 0.2 mM CaCl 2 , 40 mM Na 4 P 2 O 7 , 50 mM NaF, 5 mM MgCl 2 , 0.1 mM Na 3 VO 4 , 10 mM EDTA, 1% Triton X100, 0.5% sodium deoxycholate, 0.1% SDS and 1 tablet Boehringer Mannheim complete protease inhibitor/90 ml). The lysates were treated as previously described (31). Essentially, ERKs were immunoprecipitated from each lysate using the rabbit polyclonal ERK antibody K-23 (Santa Cruz Biotechnology).…”

“…DdERK2 activation by folic acid is dependent on the presence of heterotrimeric G-proteins (29,30). DdERK2 stimulation by cAMP, however, can take place in the absence of the single G␤ subunit (31)(32)(33), suggesting that this process is heterotrimeric G-protein-independent. Here we demonstrate that exogenous LPA induces activation of DdERK2 in aggregation competent D. discoideum cells, independent of cARs, yet dependent on the G␤ subunit of heterotrimeric G-proteins.…”

Activation of the Mitogen-activated Protein Kinase ERK2 by the Chemoattractant Folic Acid in Dictyostelium

“…This pathway is positively regulated by cAMP-dependent PKA and negatively regulated by Ras pathways (18), although another group has conflicting data on some of these points (Ref. 3; see below). ERK2 is also regulated by components of the adenylyl cyclase pathway such as CRAC (18).…”

Regulation of G protein‐coupled cAMP receptor activation by a hydrophobic residue in transmembrane helix 3

“…In the case of ACA, adaptation may be due to the transient activation of upstream Ras proteins required to activate PI3K (Sasaki et al, 2004). Although the pathway leading to ERK2 is poorly understood, Ras proteins also appear to be involved in its activation (Knetsch et al, 1996;Aubry et al, 1997). Thus, a common adaptation mechanism acting on Ras proteins might regulate both ACA and ERK2 pathways.…”