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Constitutive signal bias mediated by the human GHRHR splice variant 1.

ABSTRACT: Alternative splicing of G protein-coupled receptors has been observed, but their functions are largely unknown. Here, we report that a splice variant (SV1) of the human growth hormone-releasing hormone receptor (GHRHR) is capable of transducing biased signal. Differing only at the receptor N terminus, GHRHR predominantly activates Gs while SV1 selectively couples to β-arrestins. Based on the cryogenic electron microscopy structures of SV1 in the apo state or GHRH-bound state in complex with the Gs protein, molecular dynamics simulations reveal that the N termini of GHRHR and SV1 differentiate the downstream signaling pathways, Gs versus β-arrestins. As suggested by mutagenesis and functional studies, it appears that GHRH-elicited signal bias toward β-arrestin recruitment is constitutively mediated by SV1. The level of SV1 expression in prostate cancer cells is also positively correlated with ERK1/2 phosphorylation but negatively correlated with cAMP response. Our findings imply that constitutive signal bias may be a mechanism that ensures cancer cell proliferation.

SUBMITTER: Cong Z

PROVIDER: S-EPMC8501799 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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Constitutive signal bias mediated by the human GHRHR splice variant 1.

Cong Zhaotong Z Zhou Fulai F Zhang Chao C Zou Xinyu X Zhang Huibing H Wang Yuzhe Y Zhou Qingtong Q Cai Xiaoqing X Liu Qiaofeng Q Li Jie J Shao Lijun L Mao Chunyou C Wang Xi X Wu Jihong J Xia Tian T Zhao Li-Hua LH Jiang Hualiang H Zhang Yan Y Xu H Eric HE Cheng Xi X Yang Dehua D Wang Ming-Wei MW

Proceedings of the National Academy of Sciences of the United States of America 20211001 40

Alternative splicing of G protein-coupled receptors has been observed, but their functions are largely unknown. Here, we report that a splice variant (SV1) of the human growth hormone-releasing hormone receptor (GHRHR) is capable of transducing biased signal. Differing only at the receptor N terminus, GHRHR predominantly activates G<sub>s</sub> while SV1 selectively couples to β-arrestins. Based on the cryogenic electron microscopy structures of SV1 in the <i>apo</i> state or GHRH-bound state in ...[more]

PMID: 34599099

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Project description:BackgroundThe cytoskeletal adaptor protein vinculin plays a fundamental role in cell contact regulation and affects central aspects of cell motility, which are essential to both embryonal development and tissue homeostasis. Functional regulation of this evolutionarily conserved and ubiquitously expressed protein is dominated by a high-affinity, autoinhibitory head-to-tail interaction that spatially restricts ligand interactions to cell adhesion sites and, furthermore, limits the residency time of vinculin at these sites. To date, no mutants of the vinculin protein have been characterized in animal models.Methodology/principal findingsHere, we investigate vinculin-DeltaEx20, a splice variant of the protein lacking the 68 amino acids encoded by exon 20 of the vinculin gene VCL. Vinculin-DeltaEx20 was found to be expressed alongside with wild type protein in a knock-in mouse model with a deletion of introns 20 and 21 (VCL-DeltaIn20/21 allele) and shows defective head-to-tail interaction. Homozygous VCL-DeltaIn20/21 embryos die around embryonal day E12.5 showing cranial neural tube defects and exencephaly. In mouse embryonic fibroblasts and upon ectopic expression, vinculin-DeltaEx20 reveals characteristics of constitutive head binding activity. Interestingly, the impact of vinculin-DeltaEx20 on cell contact induction and stabilization, a hallmark of the vinculin head domain, is only moderate, thus allowing invasion and motility of cells in three-dimensional collagen matrices. Lacking both F-actin interaction sites of the tail, the vinculin-DeltaEx20 variant unveils vinculin's dynamic binding to cell adhesions independent of a cytoskeletal association, and thus differs from head-to-tail binding deficient mutants such as vinculin-T12, in which activated F-actin binding locks the protein variant to cell contact sites.Conclusions/significanceVinculin-DeltaEx20 is an active variant supporting adhesion site stabilization without an enhanced mechanical coupling. Its presence in a transgenic animal reveals the potential of splice variants in the vinculin gene to alter vinculin function in vivo. Correct control of vinculin is necessary for embryonic development.

Dataset Information

Constitutive signal bias mediated by the human GHRHR splice variant 1.

Publications

Constitutive signal bias mediated by the human GHRHR splice variant 1.

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