title: Sperm membrane protein (hSMP-1) and RanBPM complex in the microtubule-organizing centre.
abstract: hSMP-1 is a human sperm membrane protein expressed during development. It is a testis-specific component produced during male germ cell differentiation. Proteins that interact with hSMP-1 were identified by the application of the yeast two-hybrid system. One of the components, RanBPM, was found to be associated with hSMP-1 under both in vitro and in vivo conditions. In the human testis, RanBPM is produced in spermatogonia and primary spermatocytes, suggesting expression during the early stages of spermatogenesis; whereas in the rat testis, it is located in round and elongated spermatids, similar to hSMP-1, suggesting expression of both components during spermiogenesis. Images obtained by immunofluorescence and confocal scanning microscopy of CHO-K1 cells co-transfected with pEGFP-C1-hSMP-1 and pDsRed1-Nl-RanBPM revealed that RanBPM and hSMP-1 are distributed in discrete loci throughout the cytoplasm. When superimposed, the stained spots appeared as congruent yellow areas, indicative of co-localization and probable complex formation of these two components. This interaction between hSMP-1 and RanBPM may be involved in the process of male germ cell differentiation. In CHO-Kl cells transfected with pEGFP-Cl-hSMP-1, the exogenously expressed hSMP-1 was found to co-localize with alpha-tubulin. Depolymerization of microtubules can be induced in CHO-Kl cells by cold treatment. In cells transfected with the pEGFP-Cl vector, the dispersed tubulins promptly reassembled upon warming. However, in cells transfected with pEGFP-Cl-hSMP-1, reassembly of the dispersed tubulins was blocked even upon rewarming of the cells. These findings suggest that hSMP-1 interacts with tubulins and thereby may modulate microtubule assembly and/or activity.
authors.affiliation: 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, 100005 Beijing, China.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Tang
authors.forename: Jianchao
authors.initials: J
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Cai
authors.forename: Shiying
authors.initials: S
authors.lastname: Miao
authors.forename: Shudong
authors.initials: S
authors.lastname: Zong
authors.forename: S S
authors.initials: SS
authors.lastname: Koide
authors.forename: Linfang
authors.initials: L
authors.lastname: Wang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000954:Antigens, Surface; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D003598:Cytoskeletal Proteins; D018507:Gene Expression Regulation, Developmental; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D022101:Microtubule-Organizing Center / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D051381:Rats; D013091:Spermatogenesis; D013094:Spermatozoa / Q000378:metabolism*; D013737:Testis / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000954:Antigens, Surface; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; C116005:Ran binding protein 9; C099014:SPAG8 protein, human; D020931:ran GTP-Binding Protein