IMR Press / FBL / Volume 11 / Issue 2 / DOI: 10.2741/1913

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article
A sperm component, HSD-3.8 (SPAG1), interacts with G-protein beta 1 subunit and activates extracellular signal-regulated kinases (ERK)
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1 National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, 5 Dong Dan San Tiao, Beijing, 100005, People Republic of China
2 National Research Institute for Family Planning, WHO Collaboration Center for Research in Human Reproduction, 12 Da Hui Si, Beijing 100081, People’s Republic of China
3 Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Front. Biosci. (Landmark Ed) 2006, 11(2), 1679–1689; https://doi.org/10.2741/1913
Published: 1 May 2006
Abstract

HSD-3.8 cDNA (accession number AF311312) encodes a human sperm component. A 0.7 kb fragment (HSD-0.7) containing three immunological epitopes of HSD-3.8 cDNA was prepared and expressed in E. coli. Immunization of female rats with the recombinant HSD-0.7 proteins induced infertility. A cDNA fragment encoding the C-terminal 144 amino acids of human G-protein beta l subunit (Gβ1-C144) was screened by yeast two-hybrid, when HSD-0.7 segment was used as a bait. Recombinant His6-tagged-Gβ1-C144 protein was expressed in E. coli BL21 and Anti-Gβ1 serum was raised with purified Gβ1-C144. HA-tagged HSD-0.7 and FLAG-tagged Gβ1 plasmids were constructed and co-transfected into human embryonal kidney 293 cells. Two proteins were localized at superimposable sites in the cytoplasm, and they formed a complex when 500 micromol/L GDP existed. Overexpression of HSD-0.7 activated the G-protein-mediated extracellular signal-regulated kinases (ERK1/2); however, the truncated fragments of HSD-0.7, which lacked either TPR domain or P-loop, lost the ability to activate the ERK1/2 pathway. Further study revealed that the activation of ERK1/2 was protein kinase C (PKC) rather than Ras dependent. These results provide evidence that HSD-3.8 present in spermatocytes and sperm may participate in spermatogenesis and fertilization process by activating the PKC-dependent ERK1/2 signal transduction pathway.

Keywords
HSD-0.7
G-protein
extracellular signalregulated kinases (ERK)
PKC
p21Ras
tetratricopeptide repeat (TPR)
phosphate binding-loop (P-loop)
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