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Kirill Kiselyov

Publications and source records attributed to Kirill Kiselyov.

11 recordsLinked to original sources
PubMed2006

TRPpathies.

Many human diseases are caused by mutations in ion channels. Dissecting the pathogenesis of these 'channelopathies' has yielded important insights into the regulation of vital biological processes by ions and has become a productive tool of modern ion channel biology. One of the best examples of a synergism between the clinical and basic science aspects of a modern biological topic is cystic fibrosis. Not only did the identification of the ion channel mutated in cystic fibrosis pinpoint the root cause of this disease, but it also has significantly advanced our understanding of basic biological processes as diverse as protein folding and epithelial fluid and electrolyte secretion. The list of confirmed 'channelopathies' is growing and several members of the TRP family of ion channels have been implicated in human diseases such as mucolipidosis type IV (MLIV), autosomal dominant polycystic kidney disease (ADPKD), familial focal segmental glomerulosclerosis (FSG), hypomagnesemia with secondary hypocalcaemia (HSH), and several forms of cancer. Analysing pathogenesis of the diseases linked to TRP dysregulation provides an exciting means of identifying novel functions of TRP channels.

Animals↗
PubMed2006

Mitochondrial aberrations in mucolipidosis Type IV.

Mucolipidosis type IV is a genetic lysosomal storage disease associated with degenerative processes in the brain, eye, and other tissues. Mucolipidosis type IV results from mutations in the gene MCOLN1, which codes for the TRP family ion channel, mucolipin 1. The connection between lysosomal dysfunction and degenerative processes in mucolipidosis type IV is unclear. Here we report that mucolipidosis type IV and several unrelated lysosomal storage diseases are associated with significant mitochondrial fragmentation and decreased mitochondrial Ca2+ buffering efficiency. The mitochondrial alterations observed in these lysosomal storage diseases are reproduced in control cells by treatment with lysosomal inhibitors and with the autophagy inhibitor 3-methyladenine. This suggests that inefficient autophagolysosomal recycling of mitochondria generates fragmented, effete mitochondria in mucolipidosis. Mitochondria accumulate that cannot properly buffer calcium fluxes in the cell. A decrease in mitochondrial Ca2+ buffering capacity in cells affected by these lysosomal storage diseases is associated with increased sensitivity to apoptosis induced by Ca2+-mobilizing agonists and executed via a caspase-8-dependent pathway. Deficient Ca2+ homeostasis may represent a common mechanism of degenerative cell death in several lysosomal storage diseases.

Adenine↗
PubMed2006

Calcium signaling complexes in microdomains of polarized secretory cells.

The highly polarized nature of epithelial cells in exocrine glands necessitates targeting, assembly into complexes and confinement of the molecules comprising the Ca(2+) signaling apparatus, to cellular microdomains. Such high degree of polarized localization has been shown for all Ca(2+) signaling molecules tested, including G protein coupled receptors and their associated proteins, Ca(2+) pumps, Ca(2+) influx channels at the plasma membrane and Ca(2+) release channels in the endoplasmic reticulum. Although the physiological significance of polarized Ca(2+) signaling is clear, little is known about the mechanism of targeting, assembly and retention of Ca(2+) signaling complexes in cellular microdomains. The present review attempts to summarize the evidence in favor of polarized expression of Ca(2+) signaling proteins at the apical pole of secretory cells with emphasis on the role of scaffolding proteins in the assembly and function of the Ca(2+) signaling complexes. The consequence of polarized enrichment of Ca(2+) signaling complexes at the apical pole is generation of an apical to basal pole gradient of cell responsiveness that, at low physiological agonist concentrations, limits Ca(2+) spikes to the apical pole, and when a Ca(2+) wave occurs, it always propagates from the apical to the basal pole. Our understanding of Ca(2+) signaling in microdomains is likely to increase rapidly with the application of techniques to controllably and selectively disrupt components of the complexes and apply high resolution recording techniques, such as TIRF microscopy to this problem.

Animals↗
PubMed2006

Homer 1 mediates store- and inositol 1,4,5-trisphosphate receptor-dependent translocation and retrieval of TRPC3 to the plasma membrane.

Store-operated Ca(2+) channels (SOCs) mediate receptor-stimulated Ca(2+) influx. Accumulating evidence indicates that members of the transient receptor potential (TRP) channel family are components of SOCs in mammalian cells. Agonist stimulation activates SOCs and TRP channels directly and by inducing translocation of channels in intracellular vesicles to the plasma membrane (PM). The mechanism of TRP channel translocation in response to store depletion and agonist stimulation is not known. Here we use TRPC3 as a model to show that IP(3) and the scaffold Homer 1 (H1) regulate the rate of translocation and retrieval of TRPC3 from the PM. In resting cells, TRPC3 exists in TRPC3-H1b/c-IP(3)Rs complexes that are located in part at the PM and in part in intracellular vesicles. Binding of IP(3) to the IP(3)Rs dissociates the interaction between IP(3)Rs and H1 but not between H1 and TRPC3 to form IP(3)Rs-TRPC3-H1b/c. TIRFM and biotinylation assays show robust receptor- and store-dependent translocation of the TRPC3 to the PM and their retrieval upon termination of cell stimulation. The translocation requires depletion of stored Ca(2+) and is prevented by inhibition of the IP(3)Rs. In HEK293, dissociating the H1b/c-IP(3)R complex with H1a results in TRPC3 translocation to the PM, where it is spontaneously active. The TRPC3-H1b/c-IP(3)Rs complex is reconstituted by infusing H1c into these cells. Reconstitution is inhibited by IP(3). Deletion of H1 in mice markedly reduces the rates of translocation and retrieval of TRPC3. Conversely, infusion of H1c into H1(-/-) cells eliminates spontaneous channel activity and increases the rate of channel activation by agonist stimulation. The effects of H1c are inhibited by IP(3). These findings together with our earlier studies demonstrating gating of TRPC3 by IP(3)Rs were used to develop a model in which assembly of the TRPC3-H1b/c-IP(3)Rs complexes by H1b/c mediates both the translocation of TRPC3-containing vesicles to the PM and gating of TRPC3 by IP(3)Rs.

Animals↗
PubMed2005

TRP-ML1 regulates lysosomal pH and acidic lysosomal lipid hydrolytic activity.

Mucolipidosis type IV (MLIV) is caused by mutations in the ion channel mucolipin 1 (TRP-ML1). MLIV is typified by accumulation of lipids and membranous materials in intracellular organelles, which was hypothesized to be caused by the altered membrane fusion and fission events. How mutations in TRP-ML1 lead to aberrant lipolysis is not known. Here we present evidence that MLIV is a metabolic disorder that is not associated with aberrant membrane fusion/fission events. Thus, measurement of lysosomal pH revealed that the lysosomes in TRP-ML1(-/-) cells obtained from the patients with MLIV are over-acidified. TRP-ML1 can function as a H(+) channel, and the increased lysosomal acidification in TRP-ML1(-/-) cells is likely caused by the loss of TRP-ML1-mediated H(+) leak. Measurement of lipase activity using several substrates revealed a marked reduction in lipid hydrolysis in TRP-ML1(-/-) cells, which was rescued by the expression of TRP-ML1. Cell fractionation indicated specific loss of acidic lipase activity in TRP-ML1(-/-) cells. Furthermore, dissipation of the acidic lysosomal pH of TRP-ML1(-/-) cells by nigericin or chloroquine reversed the lysosomal storage disease phenotype. These findings provide a new mechanism to account for the pathogenesis of MLIV.

Acridine Orange↗
PubMed2005

TRP-ML1 is a lysosomal monovalent cation channel that undergoes proteolytic cleavage.

Mutations in the gene MCOLN1 coding for the TRP (transient receptor potential) family ion channel TRP-ML1 lead to the lipid storage disorder mucolipidosis type IV (MLIV). The function and role of TRP-ML1 are not well understood. We report here that TRP-ML1 is a lysosomal monovalent cation channel. Both native and recombinant TRP-ML1 are cleaved resulting in two products. Recombinant TRP-ML1 is detected as the full-length form and as short N- and C-terminal forms, whereas in native cells mainly the cleaved N and C termini are detected. The N- and C-terminal fragments of TRP-ML1 were co-immunoprecipitated from cell lysates and co-eluted from a Ni2+ column. TRP-ML1 undergoes proteolytic cleavage that is inhibited by inhibitors of cathepsin B (CatB) and is altered when TRP-ML1 is expressed in CatB-/- cells. N-terminal sequencing of purified C-terminal fragment of TRP-ML1 expressed in Sf9 cells indicates a cleavage site at Arg200 downward arrow Pro201. Consequently, the conserved R200H mutation changed the cleavage pattern of TRP-ML1. The cleavage inhibited TRP-ML1 channel activity. This work provides the first example of inactivation by cleavage of a TRP channel. The significance of the cleavage to the function of TRP-ML1 is under investigation.

Animals↗
PubMed2005

Protein-protein interaction and functionTRPC channels.

Since their identification in the concluding years of the last century, the mammalian transient receptor potential (canonical) (TRPC) channels have remained in the limelight as the primary candidates for the Ca(2+) entry pathway activated by the hormones, growth factors, and neurotransmitters that exert their effect through activation of PLC. Although TRPC channels have been shown clearly to mediate, at least in part, receptor-activated Ca(2+) entry in literally all cell types, several of their central characteristics, as recorded in expression systems using recombinant channels, differ from those of the native receptor-dependent Ca(2+) influx channels. The present review attempts to highlight the interaction of TRPC channels with other proteins, which may explain the variability of TRPC channel activation and regulatory mechanisms observed with the native and recombinant channels. These include the homologous and heterotopous interactions of TRPC channel isoforms, the interaction of TRPC channels with calmodulin, PLCgamma, IP(3) receptors, and with scaffolding proteins like InaD, EBP50/NEHRF, caveolin, Janctate and Homers.

Animals↗
PubMed2004

Agonist-induced Ca2+ entry determined by inositol 1,4,5-trisphosphate recognition.

It has been considered that Ca2+ release is the causal trigger for Ca2+ entry after receptor activation. In DT40 B cells devoid of inositol 1,4,5-trisphosphate receptors (IP3R), the lack of Ca2+ entry in response to receptor activation is attributed to the absence of Ca2+ release. We reveal in this article that IP3R recognition of IP3 determines agonist-induced Ca2+ entry (ACE), independent of its Ca2+ release activity. In DT40 IP3R(-/-) cells, endogenous ACE can be rescued with type 1 IP3R mutants (both a DeltaC-terminal truncation mutant and a D2550A pore mutant), which are defective in Ca2+ release channel activity. Thus, in response to B cell receptor activation, ACE is restored in an IP3R-dependent manner without Ca2+ store release. Conversely, ACE cannot be rescued with mutant IP3Rs lacking IP3 binding (both the Delta90-110 and R265Q IP3-binding site mutants). We conclude that an IP3-dependent conformational change in the IP3R, not endoplasmic reticulum Ca2+ pool release, triggers ACE.

Amino Acid Substitution↗
PubMed2003

Homer binds TRPC family channels and is required for gating of TRPC1 by IP3 receptors.

Receptor signaling at the plasma membrane often releases calcium from intracellular stores. For example, inositol triphosphate (IP3) produced by receptor-coupled phospholipase C activates an intracellular store calcium channel, the IP(3)R. Conversely, stores can induce extracellular calcium to enter the cell through plasma membrane channels, too. How this "reverse" coupling works was unclear, but store IP(3)Rs were proposed to bind and regulate plasma membrane TRP cation channels. Here, we demonstrate that the adaptor protein, termed Homer, facilitates a physical association between TRPC1 and the IP(3)R that is required for the TRP channel to respond to signals. The TRPC1-Homer-IP(3)R complex is dynamic and its disassembly parallels TRPC1 channel activation. Homer's action depends on its ability to crosslink and is blocked by the dominant-negative immediate early gene form, H1a. Since H1a is transcriptionally regulated by cellular activity, this mechanism can affect both short and long-term regulation of TRPC1 function.

Animals↗
PubMed2003

Signalling specificity in GPCR-dependent Ca2+ signalling.

Cells use signalling networks to translate with high fidelity extracellular signals into specific cellular functions. Signalling networks are often composed of multiple signalling pathways that act in concert to regulate a particular cellular function. In the centre of the networks are the receptors that receive and transduce the signals. A versatile family of receptors that detect a remarkable variety of signals are the G protein-coupled receptors (GPCRs). Virtually all cells express several GPCRs that use the same biochemical machinery to transduce their signals. Considering the specificity and fidelity of signal transduction, a central question in cell signalling is how signalling specificity is achieved, in particular among GPCRs that use the same biochemical machinery. Ca(2+) signalling is particularly suitable to address such questions, since [Ca(2+)](i) can be recorded with excellent spatial and temporal resolutions in living cells and tissues and now in living animals. Ca(2+) is a unique second messenger in that both biochemical and biophysical components form the Ca(2+) signalling complex to regulate its concentration. Both components act in concert to generate repetitive [Ca(2+)](i) oscillations that can be either localized or in the form of global, propagating Ca(2+) waves. Most of the key proteins that form Ca(2+) signalling complexes are known and their activities are reasonably well understood on the biochemical and biophysical levels. We review here the information gained from studying Ca(2+) signalling by GPCRs to gain further understanding of the mechanisms used to generate cellular signalling specificity.

Animals↗