Cyclic nucleotide-gated channels on the flagellum control Ca2+ entry into sperm.
Cyclic nucleotide-gated (CNG) channels are key elements of cGMP- and cAMP-signaling pathways in vertebrate photoreceptor cells and in olfactory sensory neurons, respectively. These channels form heterooligomeric complexes composed of at least two distinct subunits (alpha and beta). The alpha subunit of cone photoreceptors is also present in mammalian sperm. Here we identify one short and several long less abundant transcripts of beta subunits in testis. The alpha and beta subunits are expressed in a characteristic temporal and spatial pattern in sperm and precursor cells. In mature sperm, the alpha subunit is observed along the entire flagellum, whereas the short beta subunit is restricted to the principal piece of the flagellum. These findings suggest that different forms of CNG channels coexist in the flagellum. Confocal microscopy in conjunction with the Ca2+ indicator Fluo-3 shows that the CNG channels serve as a Ca2+ entry pathway that responds more sensitively to cGMP than to cAMP. Assuming that CNG channel subtypes differ in their Ca2+ permeability, dissimilar localization of alpha and beta subunits may give rise to a pattern of Ca2+ microdomains along the flagellum, thereby providing the structural basis for control of flagellar bending waves.
Forschungsinstitut für Molekulare Pharmakologie, D-10315 Berlin.
B
B
Wiesner
J
J
Weiner
R
R
Middendorff
V
V
Hagen
U B
UB
Kaupp
I
I
Weyand
D000595:Amino Acid Sequence; D000814:Aniline Compounds; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005456:Fluorescent Dyes; D015870:Gene Expression; D007150:Immunohistochemistry; D017136:Ion Transport; D008297:Male; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D013082:Sperm Tail / Q000378:metabolism*; D013737:Testis / Q000378:metabolism; D014966:Xanthenes
D000814:Aniline Compounds; D015220:Calcium Channels; D017931:DNA Primers; D018076:DNA, Complementary; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium