Cysteine String Protein (CSP) Inhibition of N-type Calcium Channels Is Blocked by Mutant Huntingtin

Miller, Linda C.; Swayne, Leigh Anne; Chen, Lina; Feng, Zhong‐Ping; Wacker, Jennifer L.; Muchowski, Paul J.; Zamponi, Gerald W.; Braun, Janice E. A.

doi:10.1074/jbc.m306230200

Cited by 47 publications

(43 citation statements)

References 57 publications

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“…Various chaperones have been shown to interact and regulate the activity of ion channels of the plasma membrane [38,39]. Furthermore, chaperones have been shown to inhibit the activity of ion channels through a direct interaction or by interacting with intermediate partners [40,41]. In addition, stomatin, a homologue of SLP-2, is known to interact and negatively regulate mechanoreceptors, the ASIC3 channels in mammalian cells [17] and MEC4 in C. elegans [15,16].…”

Section: Discussionmentioning

confidence: 99%

SLP-2 negatively modulates mitochondrial sodium–calcium exchange

et al. 2010

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a b s t r a c tMitochondria play a major role in cellular calcium homeostasis. Despite decades of studies, the molecules that mediate and regulate the transport of calcium ions in and out of the mitochondrial matrix remain unknown. Here, we investigate whether SLP-2, an inner membrane mitochondrial protein of unknown function, modulates the activity of mitochondrial Ca 2+ transporters. In HeLa cells depleted of SLP-2, the amplitude and duration of mitochondrial Ca 2+ elevations evoked by agonists were decreased compared to control cells. SLP-2 depletion increased the rates of calcium extrusion from mitochondria. This effect disappeared upon Na + removal or addition of CGP-37157, an inhibitor of the mitochondrial Na + /Ca 2+ exchanger, and persisted in permeabilized cells exposed to a fixed cytosolic Na + and Ca 2+ concentration. The rates of mitochondrial Ca 2+ extrusion were prolonged in SLP-2 over-expressing cells, independently of the amplitude of mitochondrial Ca 2+ elevations. The amplitude of cytosolic Ca 2+ elevations was increased by SLP-2 depletion and decreased by SLP-2 over-expression. These data show that SLP-2 modulates mitochondrial calcium extrusion, thereby altering the ability of mitochondria to buffer Ca 2+ and to shape cytosolic Ca 2+ signals.

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Section: Discussionmentioning

confidence: 99%

SLP-2 negatively modulates mitochondrial sodium–calcium exchange

et al. 2010

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“…Although we do not have yet enough elements to build up a mechanistic molecular model to explain the enhanced release in R6/1 synapses, it is likely that the upregulation of two SNARE proteins (synaptobrevins and SNAP-25) might be part of the molecular changes contributing to the gain of function phenotype in neurotransmitter release. On the other hand, CSP-␣, which has been shown to interact with mutant-htt (Miller et al, 2003), is required to maintain SNAP-25 levels (Chandra et al, 2005). Both proteins, CSP-␣ and SNAP-25, become reduced in Drosophila mutants lacking the palmitoyl transferase huntingtin-interacting protein 14 (Ohyama et al, 2007;Stowers and Isacoff, 2007).…”

Section: Increased Levels Of Synaptic Snares and Csp-␣ Interestinglymentioning

confidence: 99%

Increased Neurotransmitter Release at the Neuromuscular Junction in a Mouse Model of Polyglutamine Disease

Rozas¹,

Gómez‐Sánchez²,

Tomás-Zapico³

et al. 2011

J. Neurosci.

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In Huntington's disease (HD), the expansion of polyglutamine (polyQ) repeats at the N terminus of the ubiquitous protein huntingtin (htt) leads to neurodegeneration in specific brain areas. Neurons degenerating in HD develop synaptic dysfunctions. However, it is unknown whether mutant htt impacts synaptic function in general. To investigate that, we have focused on the nerve terminals of motor neurons that typically do not degenerate in HD. Here, we have studied synaptic transmission at the neuromuscular junction of transgenic mice expressing a mutant form of htt (R6/1 mice). We have found that the size and frequency of miniature endplate potentials are similar in R6/1 and control mice. In contrast, the amplitude of evoked endplate potentials in R6/1 mice is increased compared to controls. Consistent with a presynaptic increase of release probability, synaptic depression under high-frequency stimulation is higher in R6/1 mice. In addition, no changes were detected in the size and dynamics of the recycling synaptic vesicle pool. Moreover, we have found increased amounts of the synaptic vesicle proteins synaptobrevin 1,2/VAMP 1,2 and cysteine string protein-␣, and the SNARE protein SNAP-25, concomitant with normal levels of other synaptic vesicle markers. Our results reveal that the transgenic expression of a mutant form of htt leads to an unexpected gain of synaptic function. That phenotype is likely not secondary to neurodegeneration and might be due to a primary deregulation in synaptic protein levels. Our findings could be relevant to understand synaptic toxic effects of proteins with abnormal polyQ repeats.

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“…guanine nucleotide exchange factors (GEFs), 1 guanine nucleotide dissociation inhibitors, and GTPase-activating proteins). Our previous work has identified cysteine string protein (CSP) as a novel modulator of G proteins (1)(2)(3). Although the functional parallels between CSP and established G protein modulators are evident, the molecular mechanism by which CSP regulates G proteins is not yet known.…”

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confidence: 99%

“…We have shown that CSP associates with G proteins and promotes G␤␥ inhibition of N-type Ca 2ϩ channels (1)(2)(3). N-type Ca 2ϩ channels are effectors of G␤␥ such that direct binding of G protein ␤␥ subunits to the Ca 2ϩ channel ␣ 1 subunit results in a stabilization of the deep closed states of the channel (18).…”

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confidence: 99%

Characterization of the Gαs Regulator Cysteine String Protein

Natochin

Campbell

Barren

et al. 2005

Journal of Biological Chemistry

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Cysteine string protein (CSP) is an abundant regulated secretory vesicle protein that is composed of a string of cysteine residues, a linker domain, and an Nterminal J domain characteristic of the DnaJ/Hsp40 cochaperone family. We have shown previously that CSP associates with heterotrimeric GTP-binding proteins (G proteins) and promotes G protein inhibition of N-type Ca 2؉ channels. To elucidate the mechanisms by which CSP modulates G protein signaling, we examined the effects of CSP 1-198 (full-length), CSP 1-112 , and CSP 1-82 on the kinetics of guanine nucleotide exchange and GTP hydrolysis. In this report, we demonstrate that CSP selectively interacts with G␣ s and increases steady-state GTP hydrolysis. CSP 1-198 modulation of G␣ s was dependent on Hsc70 (70-kDa heat shock cognate protein) and SGT (small glutamine-rich tetratricopeptide repeat domain protein), whereas modulation by CSP 1-112 was Hsc70-SGT-independent. CSP 1-112 preferentially associated with the inactive GDP-bound conformation of G␣ s . Consistent with the stimulation of GTP hydrolysis, CSP 1-112 increased guanine nucleotide exchange of G␣ s. The interaction of native G␣ s and CSP was confirmed by coimmunoprecipitation and showed that G␣ s associates with CSP. Furthermore, transient expression of CSP in HEK cells increased cellular cAMP levels in the presence of the ␤ 2 adrenergic agonist isoproterenol. Together, these results demonstrate that CSP modulates G protein function by preferentially targeting the inactive GDP-bound form of G␣ s and promoting GDP/GTP exchange. Our results show that the guanine nucleotide exchange activity of full-length CSP is, in turn, regulated by Hsc70-SGT.G proteins constitute a family of heterotrimeric GTP-binding proteins that act as transducers in a variety of transmembrane signaling systems. G proteins are composed of ␣, ␤, and ␥ subunits that dissociate into G␣ and G␤␥ upon activation. Activation of G proteins involves an exchange of GDP for GTP on G␣ subunits and the release of GTP-bound G␣ and G␤␥ to interact with effector molecules. Effector molecules include adenylate cyclase, phospholipases, phosphodiesterases, and ion channels. Several modulators of G proteins have been identified and are thought to play crucial roles in the kinetics of G protein signaling (e.g. guanine nucleotide exchange factors (GEFs), 1 guanine nucleotide dissociation inhibitors, and GTPase-activating proteins). Our previous work has identified cysteine string protein (CSP) as a novel modulator of G proteins (1-3). Although the functional parallels between CSP and established G protein modulators are evident, the molecular mechanism by which CSP regulates G proteins is not yet known.CSPs are secretory vesicle proteins of 34 kDa that contain three conserved domains: a J domain, a linker domain, and a cysteine string region (Fig. 1A). The J domain is a 70-amino acid region of homology shared by DnaJ (a well characterized bacterial co-chaperone) and many otherwise unrelated eukaryotic proteins. The linker domain is a 30-amino acid ...

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Cysteine String Protein (CSP) Inhibition of N-type Calcium Channels Is Blocked by Mutant Huntingtin

Cited by 47 publications

References 57 publications

SLP-2 negatively modulates mitochondrial sodium–calcium exchange

SLP-2 negatively modulates mitochondrial sodium–calcium exchange

Increased Neurotransmitter Release at the Neuromuscular Junction in a Mouse Model of Polyglutamine Disease

Characterization of the Gαs Regulator Cysteine String Protein

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