Disruption of ClC-3, a Chloride Channel Expressed on Synaptic Vesicles, Leads to a Loss of the Hippocampus

Abstract

Several plasma membrane chloride channels are well characterized, but much less is known about the molecular identity and function of intracellular Cl- channels. ClC-3 is thought to mediate swelling-activated plasma membrane currents, but we now show that this broadly expressed chloride channel is present in endosomal compartments and synaptic vesicles of neurons. While swelling-activated currents are unchanged in mice with disrupted ClC-3, acidification of synaptic vesicles is impaired and there is severe postnatal degeneration of the retina and the hippocampus. Electrophysiological analysis of juvenile hippocampal slices revealed no major functional abnormalities despite slightly increased amplitudes of miniature excitatory postsynaptic currents. Mice almost lacking the hippocampus survive and show several behavioral abnormalities but are still able to acquire motor skills.

Phosphatidylinositol-4-Kinase Type II α Is a Component of Adaptor Protein-3-derived Vesicles

“…Immunostaining of wild-type and mocha brain hippocampal sections revealed a reduction in PI4KII␣ immunoreactivity in the mossy fiber nerve terminals of the hilus (Figure 7, A-D) and CA3 region (Figure 7, E-H). These nerve terminals were previously shown to be enriched in ZnT3 (Palmiter et al, 1996) and ClC-3 (Stobrawa et al, 2001) in wild-type, but not in mocha mice (Salazar et al, 2004a). The decreased kinase immunostaining in mossy nerve terminals was not due to a "global" change in nerve terminal number or structure because VAMPII distribution and abundance were not affected by the mocha mutation (Figure 7, I and J).…”

“…Synaptic vesicles are enriched in nerve terminals, where they are continuously regenerated by membrane recycling, whereas lysosomes are selectively localized in cell bodies and dendrites and are excluded from axons and axon terminals. However, it has been shown that neuron-specific AP-3 subunits are present in axons (Seong et al, 2005) and that some membrane proteins such as TI-VAMP/VAMP7, the vacuolar proton pump, ClC3, Cln3, and the Niemann-Pick type C1 protein are present both on lysosomes and on subpopulations of axonal vesicles (Luiro et al, 2001;Stobrawa et al, 2001;Li et al, 2002;Karten et al, 2003;Muzerelle et al, 2003;Kyttala et al, 2004a,b). Interestingly, TI-VAMP/VAMP7 and Cln3 have been reported to be trafficked by AP-3-dependent mechanisms Kyttala et al, 2004b).…”

Chloride/anion channels in glial cell membranes

“…However, there is an ongoing highly controversial discussion about the ClC-3 being the molecular basis for I Cl,Vol . This channel was not found to be related to the ClC-3 family (Stobrawa et al, 2001). In contrast, alternative splicing, functional mutational analysis, antisense oligonucleotides, and intracellular application of anti-CLC-3 antibodies point to potential participation of CLC-3 or a closely related channel to I Cl,Vol .…”

Specific and essential but not sufficient roles of LRRC8A in the activity of volume-sensitive outwardly rectifying anion channel (VSOR)

“…1,2 In the 1990s, several proteins, including P-glycoprotein, pI cln , and ClC-3, were proposed as molecular identities of VSOR, [3][4][5] but none of them has survived scrutiny. [6][7][8][9][10][11][12] In 2014, 2 research groups independently reported that the leucine-rich repeat containing 8A (LRRC8A), which has 4 transmembrane domains and a leucine-rich repeat (LRR) domain at the C-terminus, is a core factor of VSOR in human cells. 13,14 They reported in common that knockdown of LRRC8A diminished endogenous VSOR currents in human cells, and such reduced currents could be rescued by introduction of exogenous LRRC8A, but overexpression of LRRC8A alone in normal cells paradoxically reduced endogenous VSOR currents.…”