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Tracing the evolution of the heterotrimeric G protein ? subunit in Metazoa.

ABSTRACT: BACKGROUND:Heterotrimeric G proteins are fundamental signaling proteins composed of three subunits, G? and a G?? dimer. The role of G? as a molecular switch is critical for transmitting and amplifying intracellular signaling cascades initiated by an activated G protein Coupled Receptor (GPCR). Despite their biochemical and therapeutic importance, the study of G protein evolution has been limited to the scope of a few model organisms. Furthermore, of the five primary G? subfamilies, the underlying gene structure of only two families has been thoroughly investigated outside of Mammalia evolution. Therefore our understanding of G? emergence and evolution across phylogeny remains incomplete. RESULTS:We have computationally identified the presence and absence of every G? gene (GNA-) across all major branches of Deuterostomia and evaluated the conservation of the underlying exon-intron structures across these phylogenetic groups. We provide evidence of mutually exclusive exon inclusion through alternative splicing in specific lineages. Variations of splice site conservation and isoforms were found for several paralogs which coincide with conserved, putative motifs of DNA-/RNA-binding proteins. In addition to our curated gene annotations, within Primates, we identified 15 retrotranspositions, many of which have undergone pseudogenization. Most importantly, we find numerous deviations from previous findings regarding the presence and absence of individual GNA- genes, nuanced differences in phyla-specific gene copy numbers, novel paralog duplications and subsequent intron gain and loss events. CONCLUSIONS:Our curated annotations allow us to draw more accurate inferences regarding the emergence of all G? family members across Metazoa and to present a new, updated theory of G? evolution. Leveraging this, our results are critical for gaining new insights into the co-evolution of the G? subunit and its many protein binding partners, especially therapeutically relevant G protein - GPCR signaling pathways which radiated in Vertebrata evolution.

SUBMITTER: Lokits AD

PROVIDER: S-EPMC5896119 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Tracing the evolution of the heterotrimeric G protein α subunit in Metazoa.

Lokits A D AD Indrischek H H Meiler J J Hamm H E HE Stadler P F PF

BMC evolutionary biology 20180411 1

<h4>Background</h4>Heterotrimeric G proteins are fundamental signaling proteins composed of three subunits, Gα and a Gβγ dimer. The role of Gα as a molecular switch is critical for transmitting and amplifying intracellular signaling cascades initiated by an activated G protein Coupled Receptor (GPCR). Despite their biochemical and therapeutic importance, the study of G protein evolution has been limited to the scope of a few model organisms. Furthermore, of the five primary Gα subfamilies, the u ...[more]

PMID: 29642851

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Project description:Background & aimsThe α subunit of the heterotrimeric G stimulatory protein (Gsa), encoded by the guanine nucleotide binding protein, α-stimulating gene (Gnas, in mice), is expressed ubiquitously and mediates receptor-stimulated production of cyclic adenosine monophosphate and activation of the protein kinase A signaling pathway. We investigated the roles of Gsa in vivo in smooth muscle cells of mice.MethodsWe performed studies of mice with Cre recombinase-mediated disruption of Gnas in smooth muscle cells (GsaSMKO and SM22-CreERT2, induced in adult mice by tamoxifen). Intestinal tissues were collected for histologic, biochemical, molecular, cell biology, and physiology analyses. Intestinal function was assessed in mice using the whole-gut transit time test. We compared gene expression patterns of intestinal smooth muscle from mice with vs without disruption of Gnas. Biopsy specimens from ileum of patients with chronic intestinal pseudo-obstruction and age-matched control biopsies were analyzed by immunohistochemistry.ResultsDisruption of Gnas in smooth muscle of mice reduced intestinal motility and led to death within 4 weeks. Tamoxifen-induced disruption of Gnas in adult mice impaired contraction of intestinal smooth muscle and peristalsis. More than 80% of these died within 3 months of tamoxifen exposure, with features of intestinal pseudo-obstruction characterized by chronic intestinal dilation and dysmotility. Gsa deficiency reduced intestinal levels of cyclic adenosine monophosphate and transcriptional activity of the cyclic adenosine monophosphate response element binding protein 1 (CREB1); this resulted in decreased expression of the forkhead box F1 gene (Foxf1) and protein, and contractile proteins, such as myosin heavy chain 11; actin, α2, smooth muscle, aorta; calponin 1; and myosin light chain kinase. We found decreased levels of Gsa, FOXF1, CREB1, and phosphorylated CREB1 proteins in intestinal muscle layers of patients with chronic intestinal pseudo-obstruction, compared with tissues from controls.ConclusionsGsa is required for intestinal smooth muscle contraction in mice, and its levels are reduced in ileum biopsies of patients with chronic intestinal pseudo-obstruction. Mice with disruption of Gnas might be used to study human chronic intestinal pseudo-obstruction.

Dataset Information

Tracing the evolution of the heterotrimeric G protein ? subunit in Metazoa.

Publications

Tracing the evolution of the heterotrimeric G protein α subunit in Metazoa.

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