NAADP and the two-pore channel protein 1 participate in the acrosome reaction in mammalian spermatozoa.
The functional relationship between the formation of hundreds of fusion pores during the acrosome reaction in spermatozoa and the mobilization of calcium from the acrosome has been determined only partially. Hence, the second messenger NAADP, promoting efflux of calcium from lysosome-like compartments and one of its potential molecular targets, the two-pore channel 1 (TPC1), were analyzed for its involvement in triggering the acrosome reaction using a TPCN1 gene-deficient mouse strain. The present study documents that TPC1 and NAADP-binding sites showed a colocalization at the acrosomal region and that treatment of spermatozoa with NAADP resulted in a loss of the acrosomal vesicle that showed typical properties described for TPCs: Registered responses were not detectable for its chemical analogue NADP and were blocked by the NAADP antagonist trans-Ned-19. In addition, two narrow bell-shaped dose-response curves were identified with maxima in either the nanomolar or low micromolar NAADP concentration range, where TPC1 was found to be responsible for activating the low affinity pathway. Our finding that two convergent NAADP-dependent pathways are operative in driving acrosomal exocytosis supports the concept that both NAADP-gated cascades match local NAADP concentrations with the efflux of acrosomal calcium, thereby ensuring complete fusion of the large acrosomal vesicle.
Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians University, 81377 München, Germany Department of Pharmacy, Ludwig-Maximilians University, 81377 München, Germany Institute for Experimental and Clinical Pharmacology and Toxicology, Albert-Ludwigs-University, 79104 Freiburg, Germany Institute for Anatomy, University of Duisburg-Essen, 45141 Essen, Germany.
Lilli
L
Arndt
Jan
J
Castonguay
Elisabeth
E
Arlt
Dorke
D
Meyer
Sami
S
Hassan
Heike
H
Borth
Susanna
S
Zierler
Gunther
G
Wennemuth
Andreas
A
Breit
Martin
M
Biel
Christian
C
Wahl-Schott
Thomas
T
Gudermann
Norbert
N
Klugbauer
Ingrid
I
Boekhoff
D000177:Acrosome / Q000187:drug effects / Q000378:metabolism*; D020101:Acrosome Reaction / Q000235:genetics; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism; D002243:Carbolines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005298:Fertility; D017353:Gene Deletion; D015870:Gene Expression; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009249:NADP / Q000031:analogs & derivatives* / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D012098:Reproduction; D015398:Signal Transduction; D013076:Sperm Count; D000097903:Two-Pore Channels
D000001:Calcimycin; D002118:Calcium; D015220:Calcium Channels; D002243:Carbolines; D009249:NADP; D010879:Piperazines; C539827:1-(3-((4-(2-fluorophenyl)piperazin-1-yl)methyl)-4-methoxyphenyl)-2,3,4,9-tetrahydro-1H-pyrido(3,4-b)indole-3-carboxylic acid; C546784:TPCN1 protein, mouse; D000097903:Two-Pore Channels; C024376:NAADP