Cloning, Expression Patterns, and Chromosome Localization of Three Human and Two Mouse Homologues of GABAA Receptor-Associated Protein

Abstract

Type A receptors of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, contain alpha, beta, delta, gamma, and rho subunits. The gamma subunit has four subtypes: gamma1, gamma2, gamma3, andgamma4. GABA(A) receptor-associated protein (GABARAP) was previously demonstrated to act as a linker protein between microtubules and the gamma2 subunit of GABA(A) receptors. However, no other linker proteins have been identified as mediating the linkage of microtubules and the remaining subunits of GABA(A) receptors. In this study we identified three human paralogues (GABARAPL1, GABARAPL2, and GABARAPL3) and two mouse orthologues (Gabarapl1 and Gabarapl2) of human GABARAP, all of which encoded 117 amino acids, as does Gabarapl. The expression patterns of GABARAPL1, GABARAPL2, and GABARAP in 16 adult tissues showed that they were expressed ubiquitously. The expression levels of GABARAPL1 as a 2.3-kb transcript were very high in brain, heart, peripheral blood leukocytes, liver, kidney, placenta, and skeletal muscle, very low in thymus and small intestine, and moderate in other tissues tested. The unique 1.35-kb transcript of GABARAPL2 was expressed at high levels in heart, brain, testis, prostate, ovary, spleen, and skeletal muscle, at very low levels in lung, thymus, and small intestine, and moderately in other tissues tested. For GABARAP, a 1.3-kb transcript was abundantly expressed in all tested tissues with small variation. The expression patterns of Gabarapl1 and Gabarapl2 w…