Connexin32/38 chimeras suggest a role for the second half of the
inner loop in gap junction gating by low ph.
Wang, Xiao Guang, and Camillo Peracchia.
Department of Pharmacology and Physiology, University of Rochester,
School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY
14642-8642, Tel. (716) 275-2201, Fax (716) 461-3259
APStracts 3:0176C, 1996.
Gap junction channels are regulated by gates that close with cytosolic
acidification and transjunctional voltage (Vj ). For identifying the
connexin (Cx) domain(s) involved in channel gating, CO2 and Vj
sensitivities of channels made of Cx38, Cx32, Cx32/38 chimeras and
Cx32 mutants were studied in Xenopus oocyte pairs. Recently, we have
reported that Cx38 is more sensitive to CO2 and Vj than Cx32, due to
differences in the connexin inner loop. To identify the responsible
inner loop domain, chimeras of Cx32/38 in which the first (I1) or the
second (I2) half of the inner loop of Cx38 replaced that of Cx32, and
I2 mutants of Cx32 were tested. The chimera Cx32/38I2 (Cx32 with I2
of Cx38) was like Cx38 in CO2 sensitivity, but like Cx32 in Vj
sensitivity. Cx32/38I1 (Cx32 with I1 of Cx38) did not express
channels. Of the three Cx32 mutants, Cx32-VH/IR (VH of Cx32 replaced
with IR of Cx38) and Cx32-WW/MC (WW of Cx32 replaced with MC of Cx38)
were like Cx32 in both CO2 and Vj sensitivity, whereas Cx32-S*T/Q*P
(S*T of Cx32 replaced with Q*P of Cx38) was closer to Cx38 in CO2
sensitivity, but behaved like Cx32 in Vj gating. The data suggest
that I1 and I2 contain domains relevant for Vj and CO2 gating,
respectively.
Received 15 April 1996; accepted in final form 24 May 1996.
APS Manuscript Number C731-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96