Zeta-sarcoglycan is a functional homologue of gamma-sarcoglycan in the formation of the sarcoglycan complex.
The sarcoglycans (SGs), transmembrane components of the dystrophin-associated glycoprotein complex, are stable and functional only when they assemble into a tetrameric complex in muscle cells. A defect in any one of the four SG members disrupts the entire SG complex (SGC) and causes limb-girdle muscular dystrophy. zeta-SG has been recently found as a transmembrane protein homologous to gamma-SG and delta-SG. To characterize zeta-SG in complex formation, we co-transfected expression vectors encoding all six SGs (alpha-, beta-, gamma-, delta-, epsilon- and zeta-SG) and dystroglycan into Chinese hamster ovary cells. Immunoprecipitation analysis showed that zeta-SG or gamma-SG formed a SGC with beta-SG and delta-SG plus alpha-SG or epsilon-SG, revealing that zeta-SG can form two types of SGCs (alpha-beta-zeta-delta or epsilon-beta-zeta-delta). This result indicates the functional resemblance of zeta-SG to gamma-SG rather than delta-SG, although phylogenetic analysis suggests that zeta-SG is evolutionally closer to delta-SG than to gamma-SG. Reverse transcription (RT)-PCR showed that the expression pattern of the transcript was almost the reciprocal of that of gamma-SG in various mouse tissues and that the zeta-SG transcript was especially abundant in the brain, suggesting that zeta-SG might play a particular role in the central nervous system.
Shiga
Kazuo
K
Department of Molecular Therapy, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8502, Japan.
Yoshioka
Hiroki
H
Matsumiya
Teruhiko
T
Kimura
Ichiro
I
Takeda
Shin'ichi
S
Imamura
Michihiro
M
D000818:Animals; D001921:Brain / Q000378:metabolism; D016466:CHO Cells; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D006224:Cricetinae; D046911:Macromolecular Substances / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D010802:Phylogeny; D049031:Sarcoglycans / Q000032:analysis / Q000145:classification* / Q000235:genetics / Q000502:physiology*; D040681:Structural Homology, Protein
D046911:Macromolecular Substances; D049031:Sarcoglycans