Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
Gap junction channels are gated by a chemical gate and two transjunctional voltage (V (j))-sensitive gates: fast and slow. Slow V (j) gate and chemical gate are believed to be the same. The slow gate closes at the negative side of V (j) and is mostly inactive without uncouplers or connexin (Cx) mutations. In contrast, our present data indicate otherwise. Oocytes expressing Cx32 were subjected to series of -100 mV V (j) pulses (12-s duration, 30-s intervals). Both peak (PK) and steady-state (SS) junctional conductances (G (j)), measured at each pulse, decreased exponentially by 50-60% (tau = approximately 1.2 min). G (j)PK dropped more dramatically, such that G (j)SS/G (j)PK increased from 0.4 to 0.6, indicating a drop in V (j) sensitivity. Less striking effects were obtained with -60 mV pulses. During recovery, G (j), measured by applying 20 mV pulses (2-s duration, 30-s intervals), slowly returned to initial values (tau = approximately 7 min). With reversal of V (j) polarity, G (j)PK briefly increased and G (j)SS/G (j)PK decreased, suggesting that V (j)-dependent hemichannel reopening is faster than hemichannel closing. Similar yet more dramatic results were obtained with COOH-terminus truncated Cx32 (Cx32-D225), a mutant believed to lack fast V (j) gating. The data indicate that the slow gate of Cx32 is active in the absence of uncouplers or mutations and displays unusual V (j) behavior. Based on previous evidence for direct calmodulin (CaM) involvement in chemical/slow gating, this may also be CaM-mediated.
Anumonwo,
The carboxyl terminal domain regulates the unitary conductance and voltage dependence of connexin40 gap junction channels.
2001, Pubmed,
Xenbase
Anumonwo,
The carboxyl terminal domain regulates the unitary conductance and voltage dependence of connexin40 gap junction channels.
2001,
Pubmed
,
Xenbase
Barrio,
Gap junctions formed by connexins 26 and 32 alone and in combination are differently affected by applied voltage.
1991,
Pubmed
,
Xenbase
Bukauskas,
Two distinct gating mechanisms in gap junction channels: CO2-sensitive and voltage-sensitive.
1997,
Pubmed
Bukauskas,
Coupling asymmetry of heterotypic connexin 45/ connexin 43-EGFP gap junctions: properties of fast and slow gating mechanisms.
2002,
Pubmed
Harris,
Emerging issues of connexin channels: biophysics fills the gap.
2001,
Pubmed
Lazrak,
Gap junction gating sensitivity to physiological internal calcium regardless of pH in Novikoff hepatoma cells.
1993,
Pubmed
Loewenstein,
Permeability of membrane junctions.
1966,
Pubmed
Moreno,
Role of the carboxyl terminal of connexin43 in transjunctional fast voltage gating.
2002,
Pubmed
,
Xenbase
Oh,
Changes in permeability caused by connexin 32 mutations underlie X-linked Charcot-Marie-Tooth disease.
1997,
Pubmed
,
Xenbase
Peracchia,
Effects of caffeine and ryanodine on low pHi-induced changes in gap junction conductance and calcium concentration in crayfish septate axons.
1990,
Pubmed
Peracchia,
Slow gating of gap junction channels and calmodulin.
2000,
Pubmed
,
Xenbase
Peracchia,
Structural correlates of gap junction permeation.
1980,
Pubmed
Peracchia,
Is the chemical gate of connexins voltage sensitive? Behavior of Cx32 wild-type and mutant channels.
1999,
Pubmed
,
Xenbase
Peracchia,
Chemical gating of gap junction channels; roles of calcium, pH and calmodulin.
2004,
Pubmed
Peracchia,
Increase in gap junction resistance with acidification in crayfish septate axons is closely related to changes in intracellular calcium but not hydrogen ion concentration.
1990,
Pubmed
Peracchia,
Inhibition of calmodulin expression prevents low-pH-induced gap junction uncoupling in Xenopus oocytes.
1996,
Pubmed
,
Xenbase
Revilla,
Molecular dissection of transjunctional voltage dependence in the connexin-32 and connexin-43 junctions.
1999,
Pubmed
,
Xenbase
Rose,
Permeability of cell junction depends on local cytoplasmic calcium activity.
1975,
Pubmed
Spray,
Gap junctional conductance is a simple and sensitive function of intracellular pH.
1981,
Pubmed
Spray,
Equilibrium properties of a voltage-dependent junctional conductance.
1981,
Pubmed
,
Xenbase
Turin,
Carbon dioxide reversibly abolishes ionic communication between cells of early amphibian embryo.
1977,
Pubmed
,
Xenbase
Wang,
Connexin 32/38 chimeras suggest a role for the second half of inner loop in gap junction gating by low pH.
1996,
Pubmed
,
Xenbase
Werner,
Gating properties of connexin32 cell-cell channels and their mutants expressed in Xenopus oocytes.
1991,
Pubmed
,
Xenbase
