This gene locus has a highly complex imprinted expression pattern. It gives rise to maternally-, paternally- and biallelically-expressed transcripts that are derived from four alternative promoters with distinct 5'exons. Some transcripts contain a differentially methylated region (DMR) within their 5' exons; such DMRs are commonly found in imprinted genes and correlate with transcript expression. An antisense transcript also exists, and this antisense transcript and one of the sense transcripts are paternally expressed, produce non-coding RNAs and may regulate imprinting in this region. In addition, one of the transcripts contains a second frame-shifted open reading frame, which encodes a structurally unrelated protein named ALEX.[6][7]
Products and functions
The GNAS locus is imprinted and encodes 5 main transcripts:
A/B transcript (Gs-α short, P63092-2), biallelic: contains an alternate 5' terminal exon (A/B or Exon 1A) and uses a downstream start codon to have a shortened amino terminal region.
STX16 deletion causes loss of methylation at the A/B exon, leading to PHP1B.
XLαs (Extra long alpha-s, Q5JWF2), paternal
ALEX (Alternative gene product encoded by XL-exon, P84996), may inhibit XLαs
NESP55 (Neuroendocrine secretory protein 55, O95467), maternal
antisense GNAS transcript (Nespas: neuroendocrine secretory protein antisense)
Binds to the PRC2 complex.[8] Abolition of expression causes abnormal methylation and imprinting loss.[9]
Alternative splicing of downstream exons is also observed, which results in different forms of the Gs-α, a key element of the classical signal transduction pathway linking receptor-ligand interactions with the activation of adenylyl cyclase and a variety of cellular responses. Multiple transcript variants have been found for this gene, but the full-length nature and/or biological validity of some variants have not been determined.
Three of the GNAS gene products, Gsα-long, Gsα-short, and XLαs, are different forms of Gsα, and differ mainly in the N-terminal region. Traditional G protein-coupled receptorsignaling proceeds primarily through Gsα-long and Gsα-short, the most abundant, ubiquitously-expressed protein products of this gene. XLαs is the "extra large" isoform, and has a very long N-terminal region with some internal repeats not well-conserved across species. The XL exon also encodes in another reading frame the protein product ALEX, an inhibitory cofactor binding to the unique domain.[10][7] The structure for GNAS is solved for the canonical P63092-1 isoform only, and little is known about what the special region of XLas or ALEX looks like.
NESP55 is a protein product completely unrelated to the GNAS protein. It undergoes extensive posttranslation processing, and is sometimes grouped as a granin.[11] Nearly nothing is known about its structure; protein structure prediction predicts a mostly disordered protein with an N-terminal globular domain made up of alpha-helices.[12][13]
Many alleles in mice have been constructed for analyzing disease associations. Mice with this gene half knocked-out and half-mutated (tm1Jop/Oedsml) display increased heart weight, increased startle reflex, and abnormalities in bone structure and mineralization;[17] some other alternations can be lethal.[18] Metabolic problems resembling pseudohypoparathyroidism are seen in heterozygous mutated (wt/Oedsml) mice.[19] Knocking out the antisense transcript is known to, at minimum, cause methylation defects.[20]
^Freson K, Hoylaerts MF, Jaeken J, Eyssen M, Arnout J, Vermylen J, Van Geet C (September 2001). "Genetic variation of the extra-large stimulatory G protein alpha-subunit leads to Gs hyperfunction in platelets and is a risk factor for bleeding". Thrombosis and Haemostasis. 86 (3): 733–8. doi:10.1055/s-0037-1616126. PMID11583302. S2CID34153703.
^Hanoune J, Defer N (April 2001). "Regulation and role of adenylyl cyclase isoforms". Annual Review of Pharmacology and Toxicology. 41 (1): 145–74. doi:10.1146/annurev.pharmtox.41.1.145. PMID11264454.
^Klattenhoff C, Montecino M, Soto X, Guzmán L, Romo X, García MA, Mellstrom B, Naranjo JR, Hinrichs MV, Olate J (May 2003). "Human brain synembryn interacts with Gsalpha and Gqalpha and is translocated to the plasma membrane in response to isoproterenol and carbachol". Journal of Cellular Physiology. 195 (2): 151–7. doi:10.1002/jcp.10300. hdl:10533/174200. PMID12652642. S2CID84975473.
Faivre L, Nivelon-Chevallier A, Kottler ML, Robinet C, Khau Van Kien P, Lorcerie B, Munnich A, Maroteaux P, Cormier-Daire V, LeMerrer M (March 2001). "Mazabraud syndrome in two patients: clinical overlap with McCune-Albright syndrome". American Journal of Medical Genetics. 99 (2): 132–6. doi:10.1002/1096-8628(2000)9999:999<00::AID-AJMG1135>3.0.CO;2-A. PMID11241472.
Raymond JR, Mukhin YV, Gelasco A, Turner J, Collinsworth G, Gettys TW, Grewal JS, Garnovskaya MN (2002). "Multiplicity of mechanisms of serotonin receptor signal transduction". Pharmacology & Therapeutics. 92 (2–3): 179–212. doi:10.1016/S0163-7258(01)00169-3. PMID11916537.
Jüppner H, Bastepe M (May 2006). "Different mutations within or upstream of the GNAS locus cause distinct forms of pseudohypoparathyroidism". Journal of Pediatric Endocrinology & Metabolism. 19 (Suppl 2): 641–6. doi:10.1515/jpem.2006.19.s2.641. PMID16789629. S2CID34302323.
Mantovani G, Spada A (December 2006). "Mutations in the Gs alpha gene causing hormone resistance". Best Practice & Research. Clinical Endocrinology & Metabolism. 20 (4): 501–13. doi:10.1016/j.beem.2006.09.001. PMID17161328.
1azs: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE
1azt: GS-ALPHA COMPLEXED WITH GTP-GAMMA-S
1cjk: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE: COMPLEX WITH ADENOSINE 5'-(ALPHA THIO)-TRIPHOSPHATE (RP), MG, AND MN
1cjt: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE: COMPLEX WITH BETA-L-2',3'-DIDEOXYATP, MN, AND MG
1cju: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE: COMPLEX WITH BETA-L-2',3'-DIDEOXYATP AND MG
1cjv: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE: COMPLEX WITH BETA-L-2',3'-DIDEOXYATP, MG, AND ZN
1cs4: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE: COMPLEX WITH 2'-DEOXY-ADENOSINE 3'-MONOPHOSPHATE, PYROPHOSPHATE AND MG
1cul: COMPLEX OF GS-ALPHA WITH THE CATALYTIC DOMAINS OF MAMMALIAN ADENYLYL CYCLASE: COMPLEX WITH 2',5'-DIDEOXY-ADENOSINE 3'-TRIPHOSPHATE AND MG
1tl7: Complex Of Gs- With The Catalytic Domains Of Mammalian Adenylyl Cyclase: Complex With 2'(3')-O-(N-methylanthraniloyl)-guanosine 5'-triphosphate and Mn
1u0h: STRUCTURAL BASIS FOR THE INHIBITION OF MAMMALIAN ADENYLYL CYCLASE BY MANT-GTP
2gvd: Complex Of Gs- With The Catalytic Domains Of Mammalian Adenylyl Cyclase: Complex With TNP-ATP and Mn
2gvz: Crystal Structure of Complex of Gs- with The Catalytic Domains of Mammalian Adenylyl Cyclase: Complex with MANT-ATP and Mn