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Gap junction channels exhibit connexin-specific permeability to cyclic nucleotides.

Kanaporis G, Mese G, Valiuniene L, White TW, Brink PR, Valiunas V - J. Gen. Physiol. (2008)

Bottom Line: However, homotypic Cx40 and homotypic Cx26 exhibited reduced cAMP permeability in comparison to Cx43.These data suggest that Cx43 permeability to cAMP results in a rapid delivery of cAMP from cell to cell in sufficient quantity before degradation by phosphodiesterase to trigger relevant intracellular responses.The data also suggest that the reduced permeability of Cx26 and Cx40 might compromise their ability to deliver cAMP rapidly enough to cause functional changes in a recipient cell.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA.

ABSTRACT
Gap junction channels exhibit connexin dependent biophysical properties, including selective intercellular passage of larger solutes, such as second messengers and siRNA. Here, we report the determination of cyclic nucleotide (cAMP) permeability through gap junction channels composed of Cx43, Cx40, or Cx26 using simultaneous measurements of junctional conductance and intercellular transfer of cAMP. For cAMP detection the recipient cells were transfected with a reporter gene, the cyclic nucleotide-modulated channel from sea urchin sperm (SpIH). cAMP was introduced via patch pipette into the cell of the pair that did not express SpIH. SpIH-derived currents (I(h)) were recorded from the other cell of a pair that expressed SpIH. cAMP diffusion through gap junction channels to the neighboring SpIH-transfected cell resulted in a five to sixfold increase in I(h) current over time. Cyclic AMP transfer was observed for homotypic Cx43 channels over a wide range of conductances. However, homotypic Cx40 and homotypic Cx26 exhibited reduced cAMP permeability in comparison to Cx43. The cAMP/K(+) permeability ratios were 0.18, 0.027, and 0.018 for Cx43, Cx26, and Cx40, respectively. Cx43 channels were approximately 10 to 7 times more permeable to cAMP than Cx40 or Cx26 (Cx43 > Cx26 > or = Cx40), suggesting that these channels have distinctly different selectivity for negatively charged larger solutes involved in metabolic/biochemical coupling. These data suggest that Cx43 permeability to cAMP results in a rapid delivery of cAMP from cell to cell in sufficient quantity before degradation by phosphodiesterase to trigger relevant intracellular responses. The data also suggest that the reduced permeability of Cx26 and Cx40 might compromise their ability to deliver cAMP rapidly enough to cause functional changes in a recipient cell.

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Summary of LY flux data versus junctional conductance for Cx43, Cx26, and Cx40 cell pairs. Each data point for Cx26 (▾) represents a recipient cell fluorescence intensity over injected cell fluorescence intensity 12 min after LY injection (Valiunas et al., 2002). The solid lines correspond to the first order regressions and the dashed lines represent confidence intervals (95%) for each plot. See text for references on derivation of regression lines for Cx40 and Cx43.
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fig6: Summary of LY flux data versus junctional conductance for Cx43, Cx26, and Cx40 cell pairs. Each data point for Cx26 (▾) represents a recipient cell fluorescence intensity over injected cell fluorescence intensity 12 min after LY injection (Valiunas et al., 2002). The solid lines correspond to the first order regressions and the dashed lines represent confidence intervals (95%) for each plot. See text for references on derivation of regression lines for Cx40 and Cx43.

Mentions: To compare cAMP transfer to LY transfer for all three connexins, using the same method of simultaneous measure of gj and LY transfer as in Valiunas et al. (2002), we determined LY permeability for Cx26-transfected HeLa cells. Fig. 6 presents a summary of data from (Valiunas et al., 2002) for Cx43 and Cx40 where the ratio of recipient cell fluorescence intensity relative to the source cell is plotted versus measured gj 12 min after introduction of LY into the source cell. The new data obtained from HeLa Cx26 cell pairs are shown as individual points (▾) and were fit by a first order regression (solid line) with a slope of 0.0035/nS. Thus, Cx26 has permeability characteristics for LY that are similar to Cx40.


Gap junction channels exhibit connexin-specific permeability to cyclic nucleotides.

Kanaporis G, Mese G, Valiuniene L, White TW, Brink PR, Valiunas V - J. Gen. Physiol. (2008)

Summary of LY flux data versus junctional conductance for Cx43, Cx26, and Cx40 cell pairs. Each data point for Cx26 (▾) represents a recipient cell fluorescence intensity over injected cell fluorescence intensity 12 min after LY injection (Valiunas et al., 2002). The solid lines correspond to the first order regressions and the dashed lines represent confidence intervals (95%) for each plot. See text for references on derivation of regression lines for Cx40 and Cx43.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2279171&req=5

fig6: Summary of LY flux data versus junctional conductance for Cx43, Cx26, and Cx40 cell pairs. Each data point for Cx26 (▾) represents a recipient cell fluorescence intensity over injected cell fluorescence intensity 12 min after LY injection (Valiunas et al., 2002). The solid lines correspond to the first order regressions and the dashed lines represent confidence intervals (95%) for each plot. See text for references on derivation of regression lines for Cx40 and Cx43.
Mentions: To compare cAMP transfer to LY transfer for all three connexins, using the same method of simultaneous measure of gj and LY transfer as in Valiunas et al. (2002), we determined LY permeability for Cx26-transfected HeLa cells. Fig. 6 presents a summary of data from (Valiunas et al., 2002) for Cx43 and Cx40 where the ratio of recipient cell fluorescence intensity relative to the source cell is plotted versus measured gj 12 min after introduction of LY into the source cell. The new data obtained from HeLa Cx26 cell pairs are shown as individual points (▾) and were fit by a first order regression (solid line) with a slope of 0.0035/nS. Thus, Cx26 has permeability characteristics for LY that are similar to Cx40.

Bottom Line: However, homotypic Cx40 and homotypic Cx26 exhibited reduced cAMP permeability in comparison to Cx43.These data suggest that Cx43 permeability to cAMP results in a rapid delivery of cAMP from cell to cell in sufficient quantity before degradation by phosphodiesterase to trigger relevant intracellular responses.The data also suggest that the reduced permeability of Cx26 and Cx40 might compromise their ability to deliver cAMP rapidly enough to cause functional changes in a recipient cell.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA.

ABSTRACT
Gap junction channels exhibit connexin dependent biophysical properties, including selective intercellular passage of larger solutes, such as second messengers and siRNA. Here, we report the determination of cyclic nucleotide (cAMP) permeability through gap junction channels composed of Cx43, Cx40, or Cx26 using simultaneous measurements of junctional conductance and intercellular transfer of cAMP. For cAMP detection the recipient cells were transfected with a reporter gene, the cyclic nucleotide-modulated channel from sea urchin sperm (SpIH). cAMP was introduced via patch pipette into the cell of the pair that did not express SpIH. SpIH-derived currents (I(h)) were recorded from the other cell of a pair that expressed SpIH. cAMP diffusion through gap junction channels to the neighboring SpIH-transfected cell resulted in a five to sixfold increase in I(h) current over time. Cyclic AMP transfer was observed for homotypic Cx43 channels over a wide range of conductances. However, homotypic Cx40 and homotypic Cx26 exhibited reduced cAMP permeability in comparison to Cx43. The cAMP/K(+) permeability ratios were 0.18, 0.027, and 0.018 for Cx43, Cx26, and Cx40, respectively. Cx43 channels were approximately 10 to 7 times more permeable to cAMP than Cx40 or Cx26 (Cx43 > Cx26 > or = Cx40), suggesting that these channels have distinctly different selectivity for negatively charged larger solutes involved in metabolic/biochemical coupling. These data suggest that Cx43 permeability to cAMP results in a rapid delivery of cAMP from cell to cell in sufficient quantity before degradation by phosphodiesterase to trigger relevant intracellular responses. The data also suggest that the reduced permeability of Cx26 and Cx40 might compromise their ability to deliver cAMP rapidly enough to cause functional changes in a recipient cell.

Show MeSH
Related in: MedlinePlus