title: Switch of PMCA4 splice variants in bovine epididymis results in altered isoform expression during functional sperm maturation.
abstract: Ca(2+) and Ca(2+)-dependent signals are essential for sperm maturation and fertilization. In mouse sperm the plasma membrane Ca(2+)-ATPase (PMCA) isoform 4 plays a crucial role in Ca(2+) transport. The two major splice variants of PMCA4 are PMCA4a and PMCA4b. PMCA4a differs from PMCA4b in the mechanism of calmodulin binding and activation. PMCA4a shows a much higher basal activity and is more effective than PMCA4b in returning Ca(2+) to resting levels. Knock-out mice carrying a PMCA4-null mutation are infertile because their sperm cannot achieve a hyperactivated state of motility. As sperm reach functional maturity during their transit through the epididymis, the expression of PMCA4a and 4b was assessed in bull testis and epididymis. Quantitative PCR revealed that PMCA4b is the major splice variant in testis, caput, and corpus epididymidis. In contrast, PMCA4a is the major splice variant in cauda epididymidis, whereas sperm are transcriptionally silent. Immunohistochemical staining using a new antibody against bovine PMCA4a located the PMCA4a to the apical membrane of the epithelium of cauda epididymidis, whereas testis, caput, and corpus epididymidis were negative. Western blotting of testis, epididymis, and sperm isolated from caput and cauda epididymidis showed a much higher level of PMCA4a in cauda epididymidis and sperm from cauda epididymidis compared with testis membranes and sperm from caput epididymidis. These findings suggest that PMCA4a is transferred to bovine sperm membranes in cauda epididymidis. This isoform switch may facilitate a higher calcium turnover in sperm necessary to traverse the female genital tract.
authors.affiliation: From the Department of Anatomy and Cell Biology, Philipps-University, 35037 Marburg, Germany,; the Department of Anesthesiology, University Hospital Düsseldorf, 40225 Düsseldorf, Germany, and. Electronic address: timo.brandenburger@med.uni-duesseldorf.de.
authors.forename: Timo
authors.initials: T
authors.lastname: Brandenburger
authors.affiliation: the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905.
authors.forename: Emanuel E
authors.initials: EE
authors.lastname: Strehler
authors.affiliation: the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905.
authors.forename: Adelaida G
authors.initials: AG
authors.lastname: Filoteo
authors.affiliation: the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905.
authors.forename: Ariel J
authors.initials: AJ
authors.lastname: Caride
authors.affiliation: From the Department of Anatomy and Cell Biology, Philipps-University, 35037 Marburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Aumüller
authors.affiliation: From the Department of Anatomy and Cell Biology, Philipps-University, 35037 Marburg, Germany.
authors.forename: Heidi
authors.initials: H
authors.lastname: Post
authors.affiliation: From the Department of Anatomy and Cell Biology, Philipps-University, 35037 Marburg, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Schwarz
authors.affiliation: From the Department of Anatomy and Cell Biology, Philipps-University, 35037 Marburg, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Wilhelm
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D004822:Epididymis / Q000166:cytology / Q000201:enzymology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D007248:Infertility, Male / Q000201:enzymology / Q000235:genetics; D017136:Ion Transport; D007527:Isoenzymes; D008297:Male; D051379:Mice; D009928:Organ Specificity / Q000502:physiology; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000096:biosynthesis* / Q000235:genetics; D013079:Sperm Maturation / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology / Q000201:enzymology*; D013737:Testis / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium