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1 Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States
2 Neuroscience, Albert Einstein College of Medicine, United States
3 Neuroscience, Albert Einstein College of Medicine, Bronx, United States
* To whom correspondence should be addressed. E-mail: fbukausk{at}aecom.yu.edu.
We examined the permeabilities of homotypic and heterotypic gap junction (GJ) channels formed of rodent connexins (Cxs) 30.2, 40, 43 and 45, which are expressed in the heart and other tissues, using fluorescent dyes differing in net charge and molecular mass. Combining fluorescent imaging and electrophysiological recordings in the same cell pairs, we evaluated the single channel permeability (P
). All homotypic channels were permeable to the anionic monovalent dye, Alexa Fluor-350 (AF350), but mCx30.2 channels exhibited a significantly lower P than the others. The anionic divalent dye, Lucifer Yellow (LY), remained permeant to Cx40, Cx43 and Cx45 channels, but transfer through mCx30.2 channels was not detected. Heterotypic channels generally exhibited Ps that were intermediate to the corresponding homotypic channels. Ps of mCx30.2/Cx40, mCx30.2/Cx43 or mCx30.2/Cx45 heterotypic channels for AF350 are similar and ~2-fold higher than P of mCx30.2 homotypic channel. Permeabilities for cationic dyes were assessed only qualitatively due to their binding to nucleic acids. All homotypic and heterotypic channel configurations were permeable to ethidium bromide and DAPI. Permeability for propidium iodide was limited only for GJ channels that contain at least one mCx30.2 hemichannel. In summary, we demonstrate that Cx40, Cx43 and Cx45 are permeant to all examined cationic and anionic dyes, while mCx30.2 demonstrate permeation restrictions for molecules with molecular mass over ~400 Da. The ratio of single channel conductance to permeability for AF350 was ~40-170- fold higher for mCx30.2 than for Cx40, Cx43 and Cx45 indicative that mCx30.2 GJs are notably more adapted to perform electrical rather than metabolic cell-cell communication.
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