Identification and characterization of a novel splice variant of beta3 subunit of GABA(A) receptor in rat testis and spermatozoa.
Gamma-aminobutyric acid type A (GABA(A)) receptors are the major sites of inhibitory action of fast synaptic neurotransmission in the brain. Their receptors are also widely distributed in peripheral and endocrine tissues. A full-length cDNA encoding a novel splice variant of beta3 subunit of GABA(A) receptor, designated as beta3t, was identified in rat testis. This isoform contains a segment, having identical amino acid sequence as the beta3 subunit of neuronal GABA(A) receptors except for a section composed of 25 different amino acid sequence in the N-terminus. Northern blot shows that this isoform is found in rat testis. The beta3t isoform mRNA was detected in germ cells in the late step of spermatogenesis by in situ hybridization assay. Results of immunohistochemical and immunocytochemical assays indicate that the beta3t isoform is expressed in rat testis and spermatozoa. To determine a possible function of the N-terminal 25 amino acid segment, a recombinant plasmid of beta3t-EGFPC was constructed by fusing green fluorescent protein to the C-terminus of the beta3t isoform. The chimera product failed to be translocated unto the cell surface when expressed in HEK 293 cells; whereas, the beta3 subunit of rat brain is incorporated into the plasma membrane. In conclusion, the present results show that one variant of beta3 subunit of GABA(A) receptor, designated as beta3t, is found in germ cells of rat testis and sperm. The inability of the beta3t variant to target into the plasma membrane maybe a consequence of the unique 25 amino acid segment in the N-terminus.
Li
Shi-feng
SF
Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, PR China.
Hu
Jing-hua
JH
Yan
Yuan-chang
YC
Chen
Yu-guang
YG
Koide
S S
SS
Li
Yi-ping
YP
D017398:Alternative Splicing / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D051381:Rats; D011963:Receptors, GABA-A / Q000096:biosynthesis* / Q000235:genetics; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000378:metabolism*
C546273:GABRB3 protein, human; C546276:Gabrb3 protein, rat; D011963:Receptors, GABA-A