Extracellular Matrix Regulates Neuronal Chloride Concentration via K+-Cl--Cotransporter 2

The neuronal intracellular chloride concentration [Cl-]i is critical for {gamma}-aminobutyric acid type A (GABAA) receptor-mediated transmission. Degradation of the extracellular matrix (ECM) is associated with raised [Cl-]I but neither the mechanisms underlying this effect nor the consequences for GABA- mediated transmission are well understood. Hitherto it has been unclear how to reconcile the effect of the ECM on [Cl-]i with the established role of cation-chloride cotransporters in setting [Cl-]I. In the present work we clarify the role of the ECM in the control of neuronal [Cl-]i. By measuring [Cl-]i in central neurons from male rats we show that the ECM affects basal [Cl-]i as well as the rate of Cl- extrusion after a high load. The mechanism is not via impermeant anions but through regulation of K+-Cl--cotransporter 2 (KCC2). ECM degradation is accompanied by an N-type Ca2+-channel- and calpain-dependent reduction in the amount of KCC2 protein, increased basal [Cl-]i, reduced Cl- extrusion capacity as well as by reduced inhibitory, or even an excitatory, effect of intense GABAA- receptor mediated trans mission. This implies a previously unrecognized pathway for the control of neuronal [Cl-]i and excitability by the ECM. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=144 SRC="FIGDIR/small/527837v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1ee0d30org.highwire.dtl.DTLVardef@1a3eb1aorg.highwire.dtl.DTLVardef@a00b44org.highwire.dtl.DTLVardef@143b43f_HPS_FORMAT_FIGEXP M_FIG C_FIG