Identification of cDNA encoding an additional. alpha. subunit of a human GTP-binding protein: Expression of three. alpha. sub i subtypes in human tissues and cell lines

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 85:12
• Main Authors: Kim, S., Ang, S.L., Bloch, D.B., Bloch, K.D., Kawahara, Y., Tolman, C., Lee, R., Seidman, J.G., Neer, E.J.
• Format: Journal Article
• Language: English
• Published: United States 01.06.1988
• Subjects: 550201 - Biochemistry- Tracer Techniques; AMINES; AMINO ACID SEQUENCE; ANIMALS; AROMATICS; AZAARENES; BASIC BIOLOGICAL SCIENCES; BIOCHEMISTRY; CELL CONSTITUENTS; CELL MEMBRANES; CHEMISTRY; CYCLASES; DNA; DNA SEQUENCING; ELECTROPHORESIS; ENZYME INHIBITORS; ENZYMES; GUANINE; HETEROCYCLIC COMPOUNDS; HYDROXY COMPOUNDS; LYASES; MAMMALS; MAN; MEMBRANE PROTEINS; MEMBRANES; MESSENGER-RNA; MOLECULAR STRUCTURE; NUCLEIC ACIDS; NUCLEOTIDES; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PEPTIDES; POLYPEPTIDES; PRIMATES; PROTEINS; PURINES; RECEPTORS; RECOMBINANT DNA; RNA; STRUCTURAL CHEMICAL ANALYSIS; VERTEBRATES
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.85.12.4153

The guanine nucleotide-binding proteins (G proteins), which mediate hormonal regulation of many membrane functions, are composed of {alpha}, {beta}, and {gamma} subunits. The authors have cloned and characterized cDNA from a human T-cell library encoding a form of {alpha}{sub i} that is different from the human {alpha}{sub i} subtypes previously reported. {alpha}{sub i} is the {alpha} subunit of a class of G proteins that inhibits adenylate cyclase and regulates other enzymes and ion channels. This cDNA encodes a polypeptide of 354 amino acids and is assigned to encode the {alpha}{sub i-3} subtype of G proteins on the basis of its similarity to other {alpha}{sub i}-like cDNAs and the presence of a predicted site for ADP ribosylation by pertussis toxin. They have determined the expression of mRNA for this and two other subtypes of human {alpha}{sub i} ({alpha}{sub i-1} and {alpha}{sub i-2}) in a variety of human fetal tissues and in human cell lines. All three {alpha}{sub i} subtypes were present in the tissues tested. However, analysis of individual cell types reveals specificity of {alpha}{sub i-1} expression. mRNA for {alpha}{i-1} is absent in T cells, B cells, and monocytes but is present in other cell lines. The finding of differential expression of {alpha}{sub i-1} genes may permit characterization of distinct physiological roles for this {alpha}{sub i} subunit. mRNA for {alpha}{sub i-2} and {alpha}{sub i-3} was found in all the primary and transformed cell lines tested. Thus, some cells contain all three {alpha}{sub i} subtypes. This observation raises the question of how cells prevent cross talk among receptors that are coupled to effectors through such similar {alpha} proteins.