Molecular Cloning and Functional Expression of Mouse Connexin-30,a Gap Junction Gene Highly Expressed in Adult Brain and Skin

Edgar Dahl,Dieter Manthey,Ye Chen,Hans-Jürgen Schwarz,Young Sook Chang,Peter A Lalley,Bruce J Nicholson,Klaus Willecke

doi:10.1074/jbc.271.30.17903

Abstract

A new gap junction gene isolated from the mouse genome codes for a connexin protein of 261 amino acids. Because of its theoretical molecular mass of 30.366 kDa, it is named connexin-30. Within the connexin gene family, this protein is most closely related to connexin-26 (77% amino acid sequence identity). The coding region of mouse connexin-30 is uninterrupted by introns and is detected in the mouse genome as a single copy gene that is assigned to mouse chromosome 14 by analysis of mouse x hamster somatic cell hybrids. Abundant amounts of connexin-30 mRNA (two transcripts of 2.0 and 2.3 kilobase pairs) were found after 4 weeks of postnatal development in mouse brain and skin. Microinjection of connexin-30 cRNA into Xenopus oocytes induced formation of functional gap junction channels that gated somewhat asymmetrically in response to transjunctional voltage and at significantly lower voltage (Vo = +38 and -46 mV) than the closely homologous connexin-26 channels (Vo = 89 mV). Heterotypic pairings of connexin-30 with connexin-26 and connexin-32 produced channels with highly asymmetric and rectifying voltage gating, respectively. This suggests that the polarity of voltage gating and the cationic selectivity of connexin-30 are similar to those of its closest homologue, connexin-26.

Highlights

A new gap junction gene isolated from the mouse genome codes for a connexin protein of 261 amino acids
Cloned connexin (Cx)1 genes have been functionally expressed in Xenopus oocytes and cultured mammalian cells (reviewed by Paul (1995) and White et al (1995))
We describe the characterization of Cx30, a new member of the murine connexin gene family, which is highly expressed in adult skin and brain, but is not detected in embryonic and fetal brain

Summary

Introduction

A new gap junction gene isolated from the mouse genome codes for a connexin protein of 261 amino acids. The connexin gene family codes for the protein subunits of gap junction channels that mediate direct diffusion of ions and metabolites between the cytoplasm of adjacent cells (reviewed by Bennett et al (1991), Beyer (1993), Paul (1995), and White et al (1995)). Cloned connexin (Cx) genes have been functionally expressed in Xenopus oocytes and cultured mammalian cells (reviewed by Paul (1995) and White et al (1995)). These reconstitution experiments have shown that gap junction channels have unique properties depending on the type of connexin(s) constituting the channel. Some combinations are compatible (e.g. Cx26 and Cx32 (Barrio et al, 1991) as well as Cx40 and Cx37 (Hennemann et al, 1992a)), while others (Cx40 and Cx43) do not form functional gap junctions in Xenopus oocytes (Bruzzone et al, 1993) or cultured mammalian cells (Elfgang et al, 1995)

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