TY - JOUR
T1 - A cAMP regulated K+-selective channel from the sea urchin sperm plasma membrane
AU - Labarca, Pedro
AU - Santi, Celia
AU - Zapata, Otilia
AU - Morales, Ezequiel
AU - Beltrán, Carmen
AU - Liévano, Arturo
AU - Darszon, Alberto
N1 - Funding Information:
This work was partially supported by CONACyT, DGAPA-UNAM and Fundacio n Andes (Program C-12777/4). A.D. is an International Scholar of the Howard Hughes Medical Institute. P.L. held a Catedra Patrimonial from CONACyT, a Catedra Pre-sidencial en Ciencias, and a John Simon Guggenheim Fellowship.
PY - 1996/3/15
Y1 - 1996/3/15
N2 - Ion channels are deeply involved in sperm physiology. In sea urchin sperm cyclic nucleotide levels increase during quimotaxis and in the acrosome reaction (AR). Although cyclic nucleotides are second messengers known to directly or indirectly modulate ion channels, it is not clear how they modulate sperm responses to the egg outer layer. Here, we describe a cAMP regulated K+-selective channel from sea urchin sperm plasma membranes fused into planar bilayers that may have a role during sea urchin sperm quimotaxis and/or the AR. Its single channel conductance in 100 mM KCl is 103 pS. In bi-ionic experiments, the channel displayed a K+/Na+ permeability ratio (P(K+)/P(Na+)) of ~5. Thus, in sea water its reversal potential would be ~ -13 mV and channel opening would depolarize spermatozoa. The channel has low open probability (P(o) = 0.8 ± 0.2% at 0 mV applied voltage) and weak voltage dependence. Channel activity is reversibly up-regulated by cAMP in the cis bilayer side, but not by cGMP. This modulation followed a single Langmuir isotherm with an apparent k(d) of 200 μM. At this concentration the channel open probability at 0 mV increased up to 11-fold. TEA+ blocked the channel only from the trans side. Also Ba2+ in trans blocked the channel in a voltage-dependent manner.
AB - Ion channels are deeply involved in sperm physiology. In sea urchin sperm cyclic nucleotide levels increase during quimotaxis and in the acrosome reaction (AR). Although cyclic nucleotides are second messengers known to directly or indirectly modulate ion channels, it is not clear how they modulate sperm responses to the egg outer layer. Here, we describe a cAMP regulated K+-selective channel from sea urchin sperm plasma membranes fused into planar bilayers that may have a role during sea urchin sperm quimotaxis and/or the AR. Its single channel conductance in 100 mM KCl is 103 pS. In bi-ionic experiments, the channel displayed a K+/Na+ permeability ratio (P(K+)/P(Na+)) of ~5. Thus, in sea water its reversal potential would be ~ -13 mV and channel opening would depolarize spermatozoa. The channel has low open probability (P(o) = 0.8 ± 0.2% at 0 mV applied voltage) and weak voltage dependence. Channel activity is reversibly up-regulated by cAMP in the cis bilayer side, but not by cGMP. This modulation followed a single Langmuir isotherm with an apparent k(d) of 200 μM. At this concentration the channel open probability at 0 mV increased up to 11-fold. TEA+ blocked the channel only from the trans side. Also Ba2+ in trans blocked the channel in a voltage-dependent manner.
UR - http://www.scopus.com/inward/record.url?scp=0029947317&partnerID=8YFLogxK
U2 - 10.1006/dbio.1996.0072
DO - 10.1006/dbio.1996.0072
M3 - Article
C2 - 8631499
AN - SCOPUS:0029947317
SN - 0012-1606
VL - 174
SP - 271
EP - 280
JO - Developmental Biology
JF - Developmental Biology
IS - 2
ER -