Co-localization of the inositol 1,4,5-trisphosphate receptor and calreticulin in the equatorial segment and in membrane bounded vesicles in the cytoplasmic droplet of human spermatozoa

Citation
S. Naaby-hansen et al., Co-localization of the inositol 1,4,5-trisphosphate receptor and calreticulin in the equatorial segment and in membrane bounded vesicles in the cytoplasmic droplet of human spermatozoa, MOL HUM REP, 7(10), 2001, pp. 923-933
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell & Developmental Biology
Journal title
MOLECULAR HUMAN REPRODUCTION
ISSN journal
1360-9947 → ACNP
Volume
7
Issue
10
Year of publication
2001
Pages
923 - 933
Database
ISI
SICI code
1360-9947(200110)7:10<923:COTI1R>2.0.ZU;2-S
Abstract
Modulation of the intracellular calcium concentration within mammalian sper matozoa is important in several prefertilization events including hyperacti vated motility and the acrosome reaction. To identify calcium binding prote ins (CBP) potentially regulating these processes, a Ca-45 overlay technique was employed on 2-D blots of human sperm extracts. Microsequencing by Edma n degradation and CAD mass spectrometry identified a relatively abundant 60 .5 kDa CBP with a pI of 4.2 as calreticulin (CRT). Immunofluorescent labell ing with anti-CRT antibodies localized CRT to the acrosome, with highest fl uorescence in the equatorial segment, and in the cytoplasmic droplets of 94 and 48% of human spermatozoa respectively. Double immunolabelling experime nts demonstrated co-localization of CRT and the inositol 1,4,5-trisphosphat e receptor (IP3R) in the acrosome, in the equatorial segment, and vesicular structures in the cytoplasmic droplets of the neck region. Electron micros copic immunogold labelling localized CRT to the equatorial segment of acros ome-reacted spermatozoa and to membrane-enclosed vesicles within the cytopl asmic droplet of both acrosome-intact and acrosome-reacted spermatozoa. Loc alization of the IP3 receptor to the CRT-containing vesicles, in the sperm neck and to the acrosome, suggests that capacitative calcium entry in human spermatozoa may be regulated from these putative calcium storage sites.