Project description:Slo2 potassium channels play important roles in neuronal function, and their mutations in humans cause epilepsies and profound cognitive defects. However, little is known how Slo2 function is regulated by other proteins. In a genetic screen for suppressors of a sluggish phenotype caused by a hyperactive C. elegans Slo2 (SLO-2), mutants of adr-1, a gene important to RNA editing, were isolated. SLO-2 current in motor neurons is substantially decreased in the mutants. However, slo-2 transcripts have no detectable RNA editing events and exhibit a similar expression level in wild type and adr-1 mutants. In contrast, mRNA level of scyl-1, which encodes an orthologue of mammalian SCYL1 (a pseudokinase), is greatly reduced in adr-1 mutants due to deficient RNA editing at a single adenosine in its 3’-UTR. SCYL-1 physically interacts with SLO-2 in neurons. Single-channel open probability of SLO-2 in neurons is reduced by ~50% in scyl-1 knockout whereas that of human Slo2.2/Slack is doubled by SCYL1 in a heterologous expression system. These results suggest that SCYL-1/SCYL1 is an evolutionarily conserved regulator of Slo2 channels.
Project description:Characterizing the impact of pharmacological and shRNA-mediated silencing of EAG2 in medulloblastoma. Medulloblastoma (MB) is the most common pediatric CNS malignancy. Previously, we demonstrated that overexpression of the ion channel EAG2, identified in a subset of histological and molecular subtypes of this disease, functionally contributes to tumor progression (PMID: 22855790). Here, we demonstrate the evolutionarily conserved function of EAG2 potassium channel in promoting brain tumor growth and metastasis, delineate downstream pathways and uncover a co-option mechanism for different potassium channels to regulate mitotic cell volume and tumor progression. We show that EAG2 potassium channel is enriched at the trailing edge of migrating MB cells to regulate local cell volume dynamics, thereby facilitating cell motility. We identify the FDA- approved antipsychotic drug thioridazine as an EAG2 channel blocker that reduces xenografted MB growth and metastasis, and present a case report of repurposing thioridazine for treating a human patient. Our findings thus illustrate the potential of targeting ion channels in cancer treatment.
Project description:Using whole-cell patch clamp recording and unbiased gene expression profiling in rat dissociated hippocampal neurons cultured at high density, we demonstrate here that chronic activity blockade induced by the sodium channel blocker tetrodotoxin leads to a homeostatic increase in action potential firing and down-regulation of potassium channel genes. In addition, chronic activity blockade reduces total potassium current, as well as protein expression and current of voltage-gated Kv1 and Kv7 potassium channels, which are critical regulators of action potential firing. Importantly, inhibition of N-Methyl-D-Aspartate receptors alone mimics the effects of tetrodotoxin, including the elevation in firing frequency and reduction of potassium channel gene expression and current driven by activity blockade, whereas inhibition of L-type voltage-gated calcium channels has no effect.
Project description:Our data demonstrate that altering the RMP of triple-negative breast cancer (TNBC) cells by manipulating potassium channels increases in vitro invasion, tumor growth, and metastasis, inducing changes in gene expression associated with cell adhesion. We describe a novel mechanism for RMP-mediated cell migration involving cadherin-11 and the MAPK pathway. Importantly, we identify a new treatment strategy for metastatic TNBC by repurposing FDA-approved potassium channel blockers. Our results provide an understanding of a mechanism by which the bioelectricity regulates cancer cell invasion and metastasis that can advance the development of a potential new class of TNBC therapeutics.
Project description:Microglia are resident immune cells of the brain and regulate its inflammatory state. In neurodegenerative diseases, microglia transition from a homeostatic state to a state referred to as disease associated microglia (DAM). DAM express higher levels of proinflammatory signaling molecules, like STAT1 and TLR2, and show transitions in mitochondrial activity toward a more glycolytic response. Inhibition of Kv1.3 decreases the proinflammatory signature of DAM, though how Kv1.3 influences the response is unknown. Our goal was to establish the potential proteins interacting with Kv1.3 during transition to DAM. We utilized TurboID, a biotin ligase, fused to Kv1.3 to evaluate the potential interacting proteins with Kv1.3 via mass spectrometry in BV-2 microglia following TLR4-mediated activation. Electrophysiology, western blotting, and flow cytometry were used to evaluate Kv1.3 channel presence and TurboID biotinylation activity. We hypothesized that Kv1.3 contains domain-specific interactors that vary during a TLR4-induced inflammatory response, some of which are dependent on the PDZ-binding domain on the C-terminus. We determined that the N-terminus of Kv1.3 is responsible for trafficking Kv1.3 to the cell surface and mitochondria (e.g. NUNDC, TIMM50). Whereas, the C-terminus interacts with immune signaling proteins in an LPS-induced inflammatory response (e.g. STAT1, TLR2, and C3). There are 70 proteins that rely on the C-terminal PDZ-binding domain to interact with Kv1.3 (e.g. ND3, Snx3, and Sun1). Overall, we highlight that the Kv1.3 potassium channel functions beyond conducting the outward flux of potassium ions in an inflammatory context and that KV1.3 modulates activity of key immune signaling proteins, such as STAT1 and C3
Project description:Calcium-activated potassium channels are important membrane proteins that help in maintaining the cellular physiology and cell signalling. Till date no Calcium-activated potassium channels have been identified in Leishmania donovani. It’s gene was cloned into pET vector and expressed in E. coli BL21 (DE3). The recombinant protein was purified using nickel affinity chromatography.
Project description:G protein-coupled receptor 37-like 1 (GPR37L1) is an orphan GPCR, and its function remains largely unknown. Here we report that Gpr37l1 and GPR37L1 are among the most highly expressed GPCR transcripts in mouse and human dorsal root ganglia (DRGs) and are selectively expressed in satellite glial cells (SGCs). Peripheral neuropathy following PTX-induced pain resulted in a downregulation of GPR37L1 plasma membrane expression in DRGs. Transgenic mice with Gpr37l1 deficiency exhibited impaired resolution of neuropathic pain symptoms following PTX-induced pain, whereas overexpression of Gpr37l1 in mouse DRGs reversed pain. GPR37L1 regulates the surface expression and function of these potassium channels. Thus, GPR37L1 in SGCs offers a new target for neuropathy protection and pain control.
Project description:G-protein-gated inward rectifying potassium channels (GIRKs) require Gβγ subunits and phosphorylated phosphatidylinositides (PIPs) for gating. Although studies have provided insight into these interactions, the mechanism of how these events are modulated by Gβγ and the binding affinity between PIPs and GIRKs remains poorly understood. Here, native ion mobility mass spectrometry is employed to directly monitor small molecule binding events to mouse GIRK2. GIRK2 binds the toxin tertiapin Q and PIPs selectively and with significantly higher affinity than other phospholipids. A mutation in GIRK2 that causes a rotation in the cytoplasmic domain, similarly to Gβγ-binding to the wild-type channel, revealed differences in the selectivity towards PIPs More specifically, PIP isoforms known to weakly activate GIRKs have decreased binding affinity. Additionally, denaturing mass spectrometry and tryptic digest liquid chromatography mass spectrometry analysis was performed to confirm phosphorylation to GIRK2.
Project description:PIP2 enhances MLKL channel activity in a direct interaction manner and this gain of function promotes both necroptosis and inflammation. Previous studies have reported that phospholipids assisted MLKL recruitment and translocation which facilitates its mediated function like liposome leaking. Here, our result support MLKL act as ion channel and is finely tuned by PIP2. In the immune process especially, PIP2, as an important modulator, promotes intracellular potassium depletion and trigger inflammation which mediated bythrough MLKL channel function. Defining the role of MLKL channel function in MLKL-induced necroptosis or other potential necroptotic models will extend our understanding of the programmed cell death and critically inform the development and testing of new disease-specific, Anti-inflammatory, therapeutic strategies.