Functional Segregation of the Highly Conserved Basic Motifs within the Third Endoloop of the Human Secretin Receptor

Chan, Kathy Yuen Yee; Pang, Ronald T.K.; Chow, Billy Kwok-Chong

doi:10.1210/endo.142.9.8389

Cited by 20 publications

(8 citation statements)

References 58 publications

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“…This is consistent with many observations indicating that the IL3 of class I receptors interacts with G␣ and G␤ subunits of G proteins and is important for signal transduction (Ref. 29 (34), and PTH1 receptor (35) signaling. Moreover, splice variants of the specific PACAP receptor PAC1 have been described with insertion of 28 -56-amino acid cassettes within IL3 (36).…”

Section: Hvpac1 Receptor Cytoplasmic Domainssupporting

confidence: 93%

Identification of Cytoplasmic Domains of hVPAC1 Receptor Required for Activation of Adenylyl Cyclase

Couvineau

Lacapère

Tan

et al. 2003

Journal of Biological Chemistry

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The VPAC1 receptor is a common receptor for vasoactive intestinal peptide (VIP) 1 and pituitary adenylate cyclase-activating peptide or PACAP (1). It mediates the actions of the two neuropeptides in a large variety of tissues through coupling to G s proteins (2) and subsequent activation of adenylyl cyclase (3). Together with the VPAC2 receptor subtype, they mediate a large array of VIP or PACAP actions on exocrine secretions, release of hormones, relaxation of muscles, metabolism, immune functions, growth control of fetuses and tumor cells, and embryonic brain development (1-5). The VPAC1 receptor belongs to the class II subfamily of G protein-coupled receptors (GPCR), which includes receptors for peptides structurally related to VIP, receptors for other peptides such as the PTH, calcitonin, or CRF (6, 7), and the so-called EGF-TM7 (8) or LNB-TM7 (9) receptors bearing unusually large and complex N-terminal extracellular domains. The VPAC1 receptor, a prototypical class II receptor, has been extensively studied by site-directed mutagenesis and molecular chimerism with respect to determination of VIP binding domains (1-3) and agonist selectivity (10, 11). These studies showed that the N-terminal extracellular domain of hVPAC1 receptor plays a crucial, although not exclusive, role in VIP binding (12). Moreover, microdomains consisting of small clusters of amino acids located in the N-terminal ectodomain (11) or at the junction of extraloop 1 and TM3 (10) were characterized as selectivity filters restricting access of VIP-related peptides to the hVPAC1 receptor. A three-dimensional model of the N-terminal ectodomain of hVPAC1 receptor has been recently developed (12). In sharp contrast, nothing is known regarding the regions of the intracellular domain of the hVPAC1 receptor involved in signal transduction e.g. adenylyl cyclase activation. More generally, the current knowledge of the coupling mechanism of class II GPCRs to signal transduction is limited as compared with that of class I GPCRs including the prototypical rhodopsin and ␤-adrenergic receptors (13). Since class II peptide receptors have low overall sequence identity with class I GPCRs and even lack the rigorously conserved residues found in the core of class I receptors including the (D/E)RY sequence, the determination of the class II receptor intracellular domains involved in coupling to signal transduction cannot be simply extrapolated from our current knowledge regarding class I GPCRs.In this context, the present study explores the structurefunction relationship of the hVPAC1 receptor for VIP-induced

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Section: Hvpac1 Receptor Cytoplasmic Domainssupporting

confidence: 93%

Identification of Cytoplasmic Domains of hVPAC1 Receptor Required for Activation of Adenylyl Cyclase

Couvineau

Lacapère

Tan

et al. 2003

Journal of Biological Chemistry

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“…This was achieved with the KLT R325A-K328A mutant that did not respond to VIP. These results, in line with previous studies performed on other members of the GPCR-B family that identified the proximal domain of IC 3 loop as essential for G s coupling and adenylate cyclase activation (Huang et al 1996, Takhar et al1996, Chan et al 2001, Couvineau et al 2003 A-K 328 A) was insensitive to GTP, indicating that the global measure of GTP effects reflects the coupling of both G s and G 16 to the receptor. The junctions of IC 3 loop are predicted to be -helical and it is assumed that the correct positioning of charged amino acids plays a crucial role in G protein interaction.…”

Section: Discussionsupporting

confidence: 89%

Effect of inactivating mutations on phosphorylation and internalization of the human VPAC2 receptor

Langer

Langlet²,

Robberecht³

2005

Journal of Molecular Endocrinology

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The VPAC 2 receptor, as all members of the G-protein-coupled receptor (GPCR)-B family, has two highly conserved motifs in the third intracellular (IC 3 ) loop: a lysine and a leucine located at the amino-terminus and two basic residues separated by a leucine and an alanine at the carboxyl-terminus. This study evaluates the involvement of those conserved amino acid sequences in VPAC 2 signal transduction and regulation. The residues were mutated into alanine and mutants were expressed in Chinese hamster ovary (CHO) cells stably transfected with G 16 and aequorin. Mutation of L310 reduced efficacy of vasoactive intestinal polypeptide (VIP) to stimulate adenylate cyclase activity through G s coupling by 75%, without affecting VIP capability to stimulate an increase in [Ca 2+ ] i through G 16 coupling. Mutation of R325 and, to a lesser extend, K328 reduced VIP efficacy to stimulate [Ca 2+ ] i increase and VIP potency to stimulate adenylate cyclase. The combination of mutations of both amino-and carboxyl-terminus located conserved motifs of the IC 3 loop generates an inactive receptor with respect to [Ca2+] i increase and adenylate cyclase activation, but also with respect to receptor phosphorylation and internalization that were indeed directly correlated with the potency of inactivation of the receptors.The amino-terminus of the VPAC 2 receptor IC 3 loop is thus involved in adenylate cyclase activation and the carboxyl-terminus of the IC 3 loop participates in both G s and G 16 coupling. The mutations studied also reduced both receptor phosphorylation and internalization in a manner that appeared directly linked to the alteration of G s and G 16 coupling.

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“…Sitedirected mutagenesis of residues in similar cytosolic face regions of these receptors has also produced loss-of-function phenotypes, but the details of the molecular basis for exposure of these regions for G protein association is currently unclear (Chan et al, 2001;Tams et al, 2001).…”

Section: Tm Receptors As Shapeshifting Proteinsmentioning

confidence: 99%

Seven Transmembrane Receptors as Shapeshifting Proteins: The Impact of Allosteric Modulation and Functional Selectivity on New Drug Discovery

2010

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Functional Segregation of the Highly Conserved Basic Motifs within the Third Endoloop of the Human Secretin Receptor

Cited by 20 publications

References 58 publications

Identification of Cytoplasmic Domains of hVPAC1 Receptor Required for Activation of Adenylyl Cyclase

Identification of Cytoplasmic Domains of hVPAC1 Receptor Required for Activation of Adenylyl Cyclase

Effect of inactivating mutations on phosphorylation and internalization of the human VPAC2 receptor

Seven Transmembrane Receptors as Shapeshifting Proteins: The Impact of Allosteric Modulation and Functional Selectivity on New Drug Discovery

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