Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 229.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 263.2 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 263.2 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 263.2 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 263.2 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 263.2 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Warning: imagejpeg(C:\Inetpub\vhosts\kidney.de\httpdocs\phplern\26324677
.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Gen+Physiol
2015 ; 146
(3
): 245-54
Nephropedia Template TP
gab.com Text
Twit Text FOAVip
Twit Text #
English Wikipedia
Glutathione release through connexin hemichannels: Implications for chemical
modification of pores permeable to large molecules
#MMPMID26324677
Tong X
; Lopez W
; Ramachandran J
; Ayad WA
; Liu Y
; Lopez-Rodriguez A
; Harris AL
; Contreras JE
J Gen Physiol
2015[Sep]; 146
(3
): 245-54
PMID26324677
show ga
Cysteine-scanning mutagenesis combined with thiol reagent modification is a
powerful method with which to define the pore-lining elements of channels and the
changes in structure that accompany channel gating. Using the Xenopus laevis
oocyte expression system and two-electrode voltage clamp, we performed
cysteine-scanning mutagenesis of several pore-lining residues of connexin 26
(Cx26) hemichannels, followed by chemical modification using a
methanethiosulfonate (MTS) reagent, to help identify the position of the gate.
Unexpectedly, we observed that the effect of MTS modification on the currents was
reversed within minutes of washout. Such a reversal should not occur unless
reducing agents, which can break the disulfide thiol-MTS linkage, have access to
the site of modification. Given the permeability to large metabolites of connexin
channels, we tested whether cytosolic glutathione (GSH), the primary cell
reducing agent, was reaching the modified sites through the connexin pore.
Inhibition of gamma-glutamylcysteine synthetase by buthionine sulfoximine
decreased the cytosolic GSH concentration in Xenopus oocytes and reduced
reversibility of MTS modification, as did acute treatment with tert-butyl
hydroperoxide, which oxidizes GSH. Cysteine modification based on thioether
linkages (e.g., maleimides) cannot be reversed by reducing agents and did not
reverse with washout. Using reconstituted hemichannels in a liposome-based
transport-specific fractionation assay, we confirmed that homomeric Cx26 and Cx32
and heteromeric Cx26/Cx32 are permeable to GSH and other endogenous reductants.
These results show that, for wide pores, accessibility of cytosolic reductants
can lead to reversal of MTS-based thiol modifications. This potential for
reversibility of thiol modification applies to on-cell accessibility studies of
connexin channels and other channels that are permeable to large molecules, such
as pannexin, CALHM, and VRAC.