The human genome encodes at least three non‐allellic G proteins with α<sub>i</sub>‐type subunits

Suki, Wadi N.; Abramowitz, Joel; Mattera, Rafael; Codina, Juan; Birnbaumer, Lutz

doi:10.1016/0014-5793(87)80900-6

Cited by 93 publications

(32 citation statements)

References 35 publications

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“…The presence of these two types of as subunits in the oocyte suggests that they may have different functions in this cell. Several G-protein regions share considerable similarity with the guanine nucleotide binding regions of elongation factor Tu and p21ras [21]. Consistent with this role, these regions (Fig.…”

Section: Discussionsupporting

confidence: 62%

Molecular cloning and sequence determination of four different cDNA species coding for α‐subunits of G proteins from Xenopus laevis oocytes

et al. 1990

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A cDNA library preprared from Xenopus laevis oocytes in λgt10 was screened with a mixture of three oligonucleotide probes designed to detect sequences found in different mammalian genes coding for a‐subunits of G‐proteins. In addition to a clone coding for a Gαo‐type subunit previously reported [(1989) FEBS Lett. 244, 188‐192] four additional clones have been found coding for different Gα protein subunits. By comparison with mammalian α‐subunits, these oocyte cDNAs correspond to two closely related Gas‐la, to a Gαi‐1 and to a Gαi‐3 species. The derived amino acid sequences showed that both Gαs species contain 379 residues, corresponding to the short species without the serine residue and with a calculated M r of 42720. The Gαi‐1 gene encodes a 354 amino acid protein with an M r, of 39000 and the Gαi‐3 encodes an incomplete open reading frame of 345 residues, lacking the first 9 amino acid residues at the NH2, terminus. All these Gα‐subunits showed high identity with their respective mammalian counterparts (75–80%), indicating a great degree of conservation through the evolution and the important cellular regulatory function that they play.

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Section: Discussionsupporting

confidence: 62%

Molecular cloning and sequence determination of four different cDNA species coding for α‐subunits of G proteins from Xenopus laevis oocytes

et al. 1990

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“…Antisera were generated against synthetic peptides according to sequences common to all pertussis-toxin substrates (antia, , , , , , serum) or specific for Gf11,2 (anti-6 serum) or Ga, (anti-a, serum) as described by Mumby et al [13]. The antiai2 serum was raised against a peptide corresponding to Gcq2 (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) as published previously 171; the antiserum of one rabbit immunized later with the same peptide sequence additionally recognized the 41-kDa Gai (anti-ai serum) as demonstrated in Results. All antisera were used at a dilution of 1 : 5000 except for antisera against Gai, which were diluted 1 : 3000.…”

Section: Sds/gel Electrophoresis Immunoblots and Antiseramentioning

confidence: 99%

Purification and characterization of subforms of the guanine‐nucleotide‐binding proteins Gα_i and Gα_o

Lang

1989

European Journal of Biochemistry

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Five different pertussis-toxin-sensitive guanine-nucleotide-binding proteins (G proteins) were purified from bovine brain. Immunochemical characterization of a subunits identified two Ga, proteins (Ga,-I and Gao-II), two 41-kDa Gai proteins (Gcri-I and G1q-11) and the 40-kDa Gai2 protein. Site-directed antisera specific for Ga, proteins did not differentiate between Ga,-I and Ga,-11. However, in situ peptide mapping using polyacrylamide gel electrophoresis revealed distinct cleavage products with different proteases for each of these proteins. Additionally comparison of Rf values demonstrated a slightly faster migration for Ga,-I1 than for Ga,-I, which is the only type of Ga, protein present in cell membranes of the neuroblastoma/glioma cell line NG 108-15. The importance of these structural differences and possible functional implications are discussed.Signal transduction from receptors to second messenger systems proceeds via guanine-nucleotide-binding proteins (G proteins) which are characterized by an a, fl and y trimeric structure; GTPase activity and the site of ADP-ribosylation by bacterial toxins is located in the a subunit which is different for each of the G-protein subtypes (for review see [l

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“…However, the arginine residue which is the target for cholera-toxin-catalyzed ADP-ribosylation in G,, is conserved in an equivalent position in Gi, subtypes [4,5,[7][8][9][10][11], G,, [4,7,12, 221 and G,, (13,141. Indeed it was shown that in the absence of GTP and in the presence of high concentrations of cholera toxin, ADP-ribosylation of 40-kDa pertussis-toxin substrates occurs in membranes from RAW264 macrophage cells [23], adipocytes [24], HL-60 myeloid cells [25] and NG108-15 neuroblastoma x glioma cells [26].…”

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confidence: 99%

Cholera toxin differentially decreases membrane levels of α and β subunits of G proteins in NG108‐15 cells

Klinz

Costa

1990

European Journal of Biochemistry

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Treatment of NG108-15 neuroblastoma x glioma cells (24 h) with cholera toxin (0.1 -10 pg/ml) resulted in a concentration-dependent reduction of the membrane levels of subunits of GTP-binding regulatory proteins (G proteins), as determined by quantitative immunoblot procedures. The extent of reduction differed for different types of subunits: the levels of Go, and G,, were reduced by 40 -So%, whereas those of Gncommon immunoreactivity and Gi2& were only reduced by 10-20% following treatment with 10 pg/ml cholera toxin. This effect of the toxin could not be mimicked by incubation with the resolved B oligomer of cholera toxin, nor by exposure of cells to agents able to raise the intracellular levels of CAMP. Basal adenylate cyclase was stimulated in a biphasic manner by cholera toxin, being stimulated at low concentrations (0.01 -10 ng/ml) and then decreased at high (0.1 -10 pg/ ml) concentrations. Thus, the down regulation of G-protein subunits produced by cholera toxin requires its (ADPribosy1)trdnsferase activity but does not result from a CAMP-mediated mechanism. The toxin-mediated decrease of Go, in the membrane was correlated with a diminution of opioid-receptor-mediated stimulation of high-affinity GTPase activity, suggesting that opioid receptors interact with Go in native membranes of NG108-15 cells.Northern-blot analysis of cytoplasmic RNA prepared from cells treated with cholera toxin showed that the levels of mRNA coding for G,, did not change. Thus, the cholera-toxin-induced decrease of G-protein subunits may not result from an alteration in mRNA levels, but may involve a direct effect of the toxin on the process of insertion and/or clearance of G proteins into and/or from the membrane. These data indicate that cholera toxin, besides catalyzing the ADP-ribosylation of G, and Gi/Go types of G proteins, can also reduce the steady state levels of Go, and Go, subunits in the membrane and thus alter by an additional mechanism the function of inhibitory receptor systems.Guanine-nucleotide-binding proteins (G proteins) couple hormone and neurotransmitter receptors to intracellular effector systems (for review see [l]). These proteins are heterotrimers in which the ct subunit binds GTP and exhibits a GTPase activity, whereas the p and y subunits are tightly associated and may serve as a membrane anchor at the inner side of the plasma membrane. The types of G proteins identified so far differ mostly in the peptide sequence of ct subunits but possess highly similar p subunits. The ct subunits vary in size over the range 39 -52 kDa and can be ADP-ribosylated by cholera toxin and/or pertussis toxin.Molecular cloning has been extensively used to identify different subunits of G proteins and to predict their aminoacid sequence. Among the a subunits studied this way, there are four forms of G,, the stimulator of adenylate cyclase [2-71, three forms of G,-type proteins putatively related to Gi, the inhibitory regulatory component of adenylate cyclase [4, 5, 7-1 I], Go, a G protein abundant in brain [4, 7, 121 and G,...

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The human genome encodes at least three non‐allellic G proteins with α_i‐type subunits

Cited by 93 publications

References 35 publications

Molecular cloning and sequence determination of four different cDNA species coding for α‐subunits of G proteins from Xenopus laevis oocytes

Molecular cloning and sequence determination of four different cDNA species coding for α‐subunits of G proteins from Xenopus laevis oocytes

Purification and characterization of subforms of the guanine‐nucleotide‐binding proteins Gα_i and Gα_o

Cholera toxin differentially decreases membrane levels of α and β subunits of G proteins in NG108‐15 cells

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The human genome encodes at least three non‐allellic G proteins with αi‐type subunits

Cited by 93 publications

References 35 publications

Molecular cloning and sequence determination of four different cDNA species coding for α‐subunits of G proteins from Xenopus laevis oocytes

Molecular cloning and sequence determination of four different cDNA species coding for α‐subunits of G proteins from Xenopus laevis oocytes

Purification and characterization of subforms of the guanine‐nucleotide‐binding proteins Gαi and Gαo

Cholera toxin differentially decreases membrane levels of α and β subunits of G proteins in NG108‐15 cells

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The human genome encodes at least three non‐allellic G proteins with α_i‐type subunits

Purification and characterization of subforms of the guanine‐nucleotide‐binding proteins Gα_i and Gα_o