Endocrinology, Vol 116, 1357-1366, Copyright © 1985 by Endocrine Society

ARTICLES

The membrane-bound spermatozoal adenylyl cyclase system does not share coupling characteristics with somatic cell adenylyl cyclases

JD Hildebrandt, J Codina, JS Tash, HJ Kirchick, L Lipschultz, RD Sekura and L Birnbaumer

Membrane-bound adenylyl cyclases from ram, dog, and human sperm are unresponsive to fluoride and guanylylimidodiphosphate [GMP-P(NH)P], two agents that stimulate the adenylyl cyclases of somatic cells by an action on the stimulatory guanine nucleotide-binding regulatory (Ns) component of adenylyl cyclase. We have investigated whether this is because the sperm cell catalytic unit is functionally uncoupled from Ns but, nevertheless, capable of interacting with it, or because the sperm cell adenylyl cyclase system is unique and regulated differently from that of somatic cells. Sperm cells were found to be deficient in Ns, as evidenced by the inability of detergent extracts from sperm cell membranes and fractions to reconstitute Ns-mediated regulation of the adenylyl cyclase of cyc- S49 cells. In addition, attempts to label Ns in sperm cell membranes by [32P]ADP ribosylation with cholera toxin revealed that, if present, Ns is less than 1% of that found in human erythrocyte membranes. This, however, was not the only reason for the unresponsiveness of sperm cell adenylyl cyclase, since fluoride stimulation of the sperm cell enzyme could not be induced by reconstituting it with Ns purified from human erythrocytes (hRBC). When intact hRBC membranes were added to sperm cell fractions in the presence of fluoride, the activities that resulted were greater than the sum of the individual activities. This apparent reconstitution of fluoride regulation of sperm cell adenylyl cyclase could be blocked by lima bean trypsin inhibitor and appears to have resulted from proteolytic activation of the hRBC adenylyl cyclase by sperm proteases. Sperm cell membranes also appear to lack a functional inhibitory regulatory protein of the adenylyl cyclase system (Ni), since they did not contain an ADP-ribosylatable substrate for pertussis toxin action. These results suggest that the sperm cell adenylyl cyclase system is unique and different from that of somatic cells. Sperm cells appear to neither contain Ns or Ni nor possess the ability of their adenylyl cyclase system to interact with Ns from an exogenous source.

This article has been cited by other articles:

				G. Livera, F. Xie, M. A. Garcia, B. Jaiswal, J. Chen, E. Law, D. R. Storm, and M. Conti Inactivation of the Mouse Adenylyl Cyclase 3 Gene Disrupts Male Fertility and Spermatozoon Function Mol. Endocrinol., May 1, 2005; 19(5): 1277 - 1290. [Abstract] [Full Text] [PDF]

				L. R. Fraser, S. A. Adeoya-Osiguwa, and R. W. Baxendale First messenger regulation of capacitation via G protein-coupled mechanisms: a tale of serendipity and discovery Mol. Hum. Reprod., December 1, 2003; 9(12): 739 - 748. [Abstract] [Full Text] [PDF]

				C. Allegrucci, L. Liguori, and A. Minelli Stimulation by N6-Cyclopentyladenosine of A1 Adenosine Receptors, Coupled to G{{alpha}}i2 Protein Subunit, Has a Capacitative Effect on Human Spermatozoa Biol Reprod, June 1, 2001; 64(6): 1653 - 1659. [Abstract] [Full Text]

				A. Darszon, P. Labarca, T. Nishigaki, and F. Espinosa Ion Channels in Sperm Physiology Physiol Rev, April 1, 1999; 79(2): 481 - 510. [Abstract] [Full Text] [PDF]

				F. Merlet, L. S. Weinstein, P. K. Goldsmith, T. Rarick, J. L. Hall, J.-P. Bisson, and P. de Mazancourt Identification and localization of G protein subunits in human spermatozoa Mol. Hum. Reprod., January 1, 1999; 5(1): 38 - 45. [Abstract] [Full Text] [PDF]