Fractional Ca(2+) current through human neuronal alpha7 nicotinic acetylcholine receptors.
The neuronal alpha7 nicotinic acetylcholine (ACh) receptor is believed to be a highly Ca(2+) permeable ligand-gated receptor-channel. However, the contribution of Ca(2+) to cationic current generated by ACh has not yet been directly measured to date. Simultaneous fluorescence and whole-cell current measurements using the Ca(2+) indicator dye fura-2 were made in GH4C1 pituitary cells stably expressing human alpha7 receptors and the fractional Ca(2+) current (the proportion of whole-cell current carried by Ca(2+); P(f)) was determined. We report that the P(f) value was 11.4+/-1.3%. This value was significantly larger than P(f) of human L248Talpha7 receptor mutant (P(f)=6.3+/-1.0%) and of rat alpha7 receptor (P(f)=8.8+/-1.5%) both determined in transiently transfected GH4C1 cells. In our knowledge, the findings here reported indicate the human alpha7 receptors are the most Ca(2+) conductive homomeric ligand-gated receptor-channels expressed in a heterologous cell system.
Fucile
Sergio
S
Istituto di Fisiologia Umana, Università di Roma "La Sapienza", P le Aldo Moro 5, I-00185 Rome, Italy. sergio.fucile@uniroma1.it
Renzi
Massimiliano
M
Lax
Pedro
P
Eusebi
Fabrizio
F
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D016257:Fura-2; D006801:Humans; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010902:Pituitary Gland; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism*; D014162:Transfection; D064569:alpha7 Nicotinic Acetylcholine Receptor
C579167:Chrna7 protein, human; C579165:Chrna7 protein, rat; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D002118:Calcium; D016257:Fura-2