scholarly journals Role of the ERC motif in the proximal part of the second intracellular loop and the C-terminal domain of the human prostaglandin F2α receptor (hFP-R) in G-protein coupling control

2005 ◽  
Vol 388 (1) ◽  
pp. 317-324 ◽  
Author(s):  
Andrea PATHE-NEUSCHÄFER-RUBE ◽  
Frank NEUSCHÄFER-RUBE ◽  
Gerhard P. PÜSCHEL

The human FP-R (F2α prostaglandin receptor) is a Gq-coupled heptahelical ectoreceptor, which is of significant medical interest, since it is a potential target for the treatment of glaucoma and preterm labour. On agonist exposure, it mediates an increase in intracellular inositol phosphate formation. Little is known about the structures that govern the agonist-dependent receptor activation. In other prostanoid receptors, the C-terminal domain has been inferred in the control of agonist-dependent receptor activation. A DRY motif at the beginning of the second intracellular loop is highly conserved throughout the G-protein-coupled receptor family and appears to be crucial for controlling agonist-dependent receptor activation. It is replaced by an ERC motif in the FP-R and no evidence for the relevance of this motif in ligand-dependent activation of prostanoid receptors has been provided so far. The aim of the present study was to elucidate the potential role of the C-terminal domain and the ERC motif in agonist-controlled intracellular signalling in FP-R mutants generated by site-directed mutagenesis. It was found that substitution of the acidic Glu132 in the ERC motif by a threonine residue led to full constitutive activation, whereas truncation of the receptor's C-terminal domain led to partial constitutive activation of all three intracellular signal pathways that had previously been shown to be activated by the FP-R, i.e. inositol trisphosphate formation, focal adhesion kinase activation and T-cell factor signalling. Inositol trisphosphate formation and focal adhesion kinase phosphorylation were further enhanced by ligand binding in cells expressing the truncation mutant but not the E132T (Glu132→Thr) mutant. Thus C-terminal truncation appeared to result in a receptor with partial constitutive activation, whereas substitution of Glu132 by threonine apparently resulted in a receptor with full constitutive activity.

2022 ◽  
Vol 12 ◽  
Author(s):  
Ian Winfield ◽  
Kerry Barkan ◽  
Sarah Routledge ◽  
Nathan J. Robertson ◽  
Matthew Harris ◽  
...  

The first intracellular loop (ICL1) of G protein-coupled receptors (GPCRs) has received little attention, although there is evidence that, with the 8th helix (H8), it is involved in early conformational changes following receptor activation as well as contacting the G protein β subunit. In class B1 GPCRs, the distal part of ICL1 contains a conserved R12.48KLRCxR2.46b motif that extends into the base of the second transmembrane helix; this is weakly conserved as a [R/H]12.48KL[R/H] motif in class A GPCRs. In the current study, the role of ICL1 and H8 in signaling through cAMP, iCa2+ and ERK1/2 has been examined in two class B1 GPCRs, using mutagenesis and molecular dynamics. Mutations throughout ICL1 can either enhance or disrupt cAMP production by CGRP at the CGRP receptor. Alanine mutagenesis identified subtle differences with regard elevation of iCa2+, with the distal end of the loop being particularly sensitive. ERK1/2 activation displayed little sensitivity to ICL1 mutation. A broadly similar pattern was observed with the glucagon receptor, although there were differences in significance of individual residues. Extending the study revealed that at the CRF1 receptor, an insertion in ICL1 switched signaling bias between iCa2+ and cAMP. Molecular dynamics suggested that changes in ICL1 altered the conformation of ICL2 and the H8/TM7 junction (ICL4). For H8, alanine mutagenesis showed the importance of E3908.49b for all three signal transduction pathways, for the CGRP receptor, but mutations of other residues largely just altered ERK1/2 activation. Thus, ICL1 may modulate GPCR bias via interactions with ICL2, ICL4 and the Gβ subunit.


2005 ◽  
Vol 280 (25) ◽  
pp. 24212-24220 ◽  
Author(s):  
Robert S. Fan ◽  
Rodrigo O. Jácamo ◽  
Xiaohua Jiang ◽  
James Sinnett-Smith ◽  
Enrique Rozengurt

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Colleen Hadley ◽  
Isin Cakir ◽  
Roger D Cone

Abstract Overweight and obesity are global concerns affecting nearly one third of the world population. These conditions are characterized by increased adiposity and are accompanied by a proportional increase in circulating leptin, an anorexigenic adipokine. Leptin is responsible for signaling peripheral energy status to the central nervous system to modulate food intake and energy expenditure. As such, neurons within the hypothalamus expressing the long isoform of leptin receptor (LepRb), a type I cytokine receptor, are primarily responsible for mediating the effects of leptin, which signal predominantly through the JAK2-STAT3 transduction mechanism. STAT3 is a latent transcription factor activated upon phosphorylation, which triggers its homodimerization and nuclear translocation. Evidence, however, for JAK2-independent, STAT3-dependent leptin receptor signaling mechanisms exist. FAK (focal adhesion kinase, Ptk2) and Pyk2 (protein tyrosine kinase 2b, Ptk2b) are a subset of nonreceptor protein tyrosine kinases and comprise the focal adhesion kinase family. FAK and Pyk2 are implicated in the regulation of cytokine receptor signaling. Furthermore, Pyk2 knockout mice have an obesity prone phenotype. Here, we studied the role of the focal adhesion kinases in leptin receptor signaling using genetic and pharmacological approaches. We found that overexpression of Pyk2 or FAK increased STAT3 phosphorylation (activation). Overexpression of a FAK or Pyk2 construct with impaired kinase activity, however, attenuated STAT3 phosphorylation, suggesting the increase in STAT3 phosphorylation is largely dependent upon kinase activity of FAK/Pyk2. Treatment of cells with a small molecule dual inhibitor of FAK and Pyk2 (PF431396) attenuated leptin-induced STAT3 phosphorylation in a mouse hypothalamic cell line. Importantly, this effect is independent of JAK2, as PF treatment of two independent JAK2-deficient cell lines exhibited similar attenuation of leptin-induced STAT3 phosphorylation. To assess the physiological relevance of FAK/Pyk2 in leptin receptor signaling in vivo, we administered PF compound to the lateral ventricle of 24-hour fasted lean wild-type mice followed by peripheral leptin administration. Intracerebroventricular (ICV) administration of PF suppressed the anorectic effect of leptin as evidenced by impaired inhibition of food intake upon refeeding. Accordingly, analysis of total hypothalamic lysates from these mice showed ICV PF impaired leptin-induced STAT3 phosphorylation. Taken together, these data suggest that Pyk2 and/or FAK play a role in leptin signal transduction.


2012 ◽  
Vol 41 (5) ◽  
pp. 1635-1642 ◽  
Author(s):  
WEN G. JIANG ◽  
LIN YE ◽  
KE JI ◽  
NATASHA FREWER ◽  
JIAFU JI ◽  
...  

1999 ◽  
Vol 145 (7) ◽  
pp. 1461-1470 ◽  
Author(s):  
Maja Oktay ◽  
Kishore K. Wary ◽  
Michael Dans ◽  
Raymond B. Birge ◽  
Filippo G. Giancotti

The extracellular matrix exerts a stringent control on the proliferation of normal cells, suggesting the existence of a mitogenic signaling pathway activated by integrins, but not significantly by growth factor receptors. Herein, we provide evidence that integrins cause a significant and protracted activation of Jun NH2-terminal kinase (JNK), while several growth factors cause more modest or no activation of this enzyme. Integrin-mediated stimulation of JNK required the association of focal adhesion kinase (FAK) with a Src kinase and p130CAS, the phosphorylation of p130CAS, and subsequently, the recruitment of Crk. Ras and PI-3K were not required. FAK–JNK signaling was necessary for proper progression through the G1 phase of the cell cycle. These findings establish a role for FAK in both the activation of JNK and the control of the cell cycle, and identify a physiological stimulus for JNK signaling that is consistent with the role of Jun in both proliferation and transformation.


Diabetes ◽  
2012 ◽  
Vol 61 (7) ◽  
pp. 1708-1718 ◽  
Author(s):  
E. P. Cai ◽  
M. Casimir ◽  
S. A. Schroer ◽  
C. T. Luk ◽  
S. Y. Shi ◽  
...  

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