Actin-Binding Properties and Colocalization with Actin During Spermiogenesis of Mammalian Sperm Calicin

• Published in: Biology of reproduction Vol. 63; no. 6; pp. 1801 - 1810
• Main Authors: LECUYER, Christophe, DACHEUX, Jean-Louis, HERMAND, Eric, MAZEMAN, Etienne, ROUSSEAUX, Jean, ROUSSEAUX-PREVOST, Roselyne
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01-12-2000; Society for the Study of Reproduction - Oxford Academic
• Subjects: Actins - metabolism; Amino Acid Sequence; Animals; Biological and medical sciences; Blotting, Western; Cell Separation; Chromatography, Gel; Chromatography, High Pressure Liquid; Computer Science; Cytoskeletal Proteins - isolation & purification; Cytoskeletal Proteins - metabolism; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Humans; In Vitro Techniques; Life Sciences; Male; Mammalian male genital system; Microfilament Proteins - metabolism; Microscopy, Fluorescence; Molecular Sequence Data; Morphology. Physiology; Sperm Head - chemistry; Sperm Head - physiology; Spermatogenesis - physiology; Spermatozoa - chemistry; Spermatozoa - metabolism; Swine; Testis - cytology; Vertebrates: reproduction; Human; Spermatozoa; Spermiogenesis; Semen; Male; Germinal cell; Testicle; Male genital system; Spermatid; Binding protein; Binding capacity; Actin; Localization
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod63.6.1801

The nucleus of mammalian spermatozoa is surrounded by a rigid layer, the perinuclear theca, which is divided into a subacrosomal
layer and a postacrosomal calyx. Among the proteins characterized in the perinuclear theca, calicin is one of the main components
of the calyx. Its sequence contains three kelch repeats and a BTB/POZ domain. We have studied the association of boar calicin
with F-actin and the distribution of boar and human calicin during spermiogenesis compared with the distribution of actin.
Calicin was purified from boar sperm heads under nondenaturating conditions. The molecule bound actin with high affinity ( K d = ∼5 nM), and a stoichiometry of approximately one calicin per 12 actin monomers was observed. Gel filtration studies showed
that calicin forms homomultimers (tetramers and higher polymers). According to immunocytochemical results, calicin is present
(together with actin) in the acrosomal region of round spermatids and is mainly localized in the postacrosomal region of late
spermatids and spermatozoa. Taken together, the results suggest that the affinity of calicin to F-actin allows targeting of
calicin at the subacrosomal space of round spermatids, and that its ability to form homomultimers contributes to the formation
of a rigid calyx.