Glialcam Affects CLC-Chloride Channels by Activating the Slow Gate

Abstract

Recently we have shown that GlialCAM, a cell adhesion molecule expressed mainly in glia, is a CLC-2 chloride channel subunit (1). Co-expression of CLC-2 with GlialCAM leads to a dramatic activation of currents and to a clustering of CLC-2 at cell contacts (1). Here we present an analysis of the interaction of GlialCAM with CLC-0 and CLC-1, two other CLC channels. CLC-1 biochemically interacts with GlialCAM and GlialCAM induces clustering of CLC-1 at cell contacts. Currents of CLC-1 and CLC-0 are modified by GlialCAM, but our study was focused mainly on CLC-0 because here slow and fast gating can be more easily separated. In particular, co-expression with GlialCAM led to an increase of the residual open-probability of the slow gate at positive voltages and the block by Zinc, which is mediated by affecting the slow gate (2) was largely reduced. In addition, deactivation of the slow gate was dramatically slowed, but retained the typical large temperature dependence (3). The mutant C212S, which lacks slow gating transitions (4), was not affected by co-expression with GlialCAM. Thus, GlialCAM is able to interact with CLC channels different from CLC-2. Our results show that in the context of CLC-0, the interaction with GlialCAM activates the slow (common) gate, suggesting that a similar mechanism underlies the activation of CLC-2. (Supported by Compagnia San Paolo and Telethon Italy (grants GGP08064 and GGP12008).)1) Jeworutzki et al. 2012 Neuron73:951.2) Chen 1998 JGP 112:715.3) Pusch et al. 1997 JGP 109:105.4) Lin et al. 1999 JGP 114:1.