Cyclic 3′,5′-AMP Causes ADAM1/ADAM2 to Rapidly Diffuse Within the Plasma Membrane of Guinea Pig Sperm1

Abstract

Because sperm cannot synthesize new proteins as they journey to the egg, they use multiple mechanisms to modify the activity of existing proteins, including changes in the diffusion coefficient of some membrane proteins. Previously, we showed that during capacitation the guinea pig heterodimeric membrane protein ADAM1/ADAM2 (fertilin) transforms from a stationary state to one of rapid diffusion within the lipid bilayer. The cause for this biophysical change, however, was unknown. In this study we examined whether an increase in cAMP, such as occurs during capacitation, could trigger this change. We incubated guinea pig cauda sperm with the membrane-permeable cAMP analog dibutyryl cAMP (db-cAMP) and the phosphodiesterase inhibitor papaverine and first tested for indications of capacitation. We observed hypermotility and acrosome-reaction competence. We then used fluorescence redistribution after photobleaching (FRAP) to measure the lateral mobility of ADAM1/ADAM2 after the db-cAMP treatment. We observed that db-cAMP caused roughly a 12-fold increase in lateral mobility of ADAM1/ADAM2, yielding diffusion similar to that observed for sperm capacitated in vitro. When we repeated the FRAP on testicular sperm incubated in db-cAMP, we found only a modest increase in lateral mobility of ADAM1/ADAM2, which underwent little redistribution. Interestingly, testicular sperm also cannot be induced to undergo capacitation. Together, the data suggests that the release of ADAM1/ADAM2 from its diffusion constraints results from a cAMP-induced signaling pathway that, like others of capacitation, is established during epididymal sperm maturation.

FRAP, FLIM, and FRET: Detection and analysis of cellular dynamics on a molecular scale using fluorescence microscopy

“…In a similar study, the presence of dibutyryl‐cAMP was found to increase the mobility of the heterodimeric guinea pig sperm membrane protein ADAM1/ADAM2 (fertilin) more than tenfold in cauda epididymal sperm but not testicular sperm. This result was similar to those found when cauda epididymal sperm were exposed to capacitating conditions (Hunnicutt et al, ).…”

“…FRAP has been applied to many developmental studies, including the original studies monitoring the behavior of acetylcholine receptors in chick myotubes (Axelrod et al, 1976b); the extent of lipid mobility in gametes (Wolf and Voglmayr, 1984;Wolf et al, 1986Wolf et al, , 1988; the distribution and dynamics of galactosyltransferase on the surface of mouse sperm (Cardullo and Wolf, 1995) and ADAM1/ ADAM2 on guinea pig sperm (Hunnicutt et al, 2008); and the formation of an acrosomal matrix during spermatogenesis in water strider sperm ( Fig. 3) (Miyata et.…”

The Annulus of the Mouse Sperm Tail Is Required to Establish a Membrane Diffusion Barrier That Is Engaged During the Late Steps of Spermiogenesis1

“…Precedence for a change in the diffusion coefficient for a sperm protein is seen with the heterodimeric sperm protein ADAM1/ADAM2 (fertilin). We previously showed that ADAM1/ADAM2 alters from an anchored state to a freely diffusing state, in this case, at the time the sperm undergoes capacitation [5,8].…”

“…Such rearrangements have been correlated with the acquisition of motility, hypermotility, capacitation, the acrosome reaction, and the sperm-egg interaction of fertilization [2][3][4][5][6][7][8][9][10][11]. Presumably, early domain segregation of many proteins ensures that the above events do not proceed prematurely.…”

Testicular and epididymal ADAMs: expression and function during fertilization

“…However, complex concentration increases in the posterior head region (and decreases in surrounding areas) when ADAM2 proteolytic processing occurs during epididymal maturation of the sperm in guinea pig. [54][55][56][57][58] Studies have identified simila rities between features of the ADAM1 and ADAM2 proteins in humans and other mammalian species, providing additional information. 29,[59][60][61][62] In mice, two intronless genes-Adam1a and Adam1b-encode different ADAM1 isoforms (Figure 2).…”