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Alexander G. PetrenkoD. sc. (chemistry) Director of departament (laboratory of receptor cell biology) Phone: E-mail: petrenkoag@gmail.com |
Education
| Period | Country, city | Education institution | Additional info |
|---|---|---|---|
| 1975–1980 | Soviet Union, Moscow | Lomonosov Moscow State University | magnum cum laude |
Selected publications
- (2011). Association of adaptor protein TRIP8b with clathrin. J. Neurochem. ,
[+]TRIP8b is a brain-specific hydrophilic cytosolic protein that contains tetratricopeptide repeats (TPRs). Previous studies revealed interaction of this protein via its TPR-containing domain with Rab8b small GTPase, HCN channels and G protein-coupled receptor CIRL. We identified clathrin as a major component of eluates from the TRIP8b affinity matrix. In the present study, by in vitro binding analysis we demonstrate a direct interaction between clathrin and TRIP8b. The clathrin-binding site was localized in the N-terminal (non-TPR containing) part of the TRIP8b molecule that contains two short motifs involved in the clathrin binding. In transfected HEK293 cells, co-expression of HCN1 with TRIP8b resulted in translocation of the channels from the cell surface to large intracellular puncta where both TRIP8b and clathrin were concentrated. These puncta co-localized partially with an early endosome marker and strongly overlapped with lysosome staining reagent. When HCN1 was co-expressed with a clathrin-non-binding mutant of TRIP8b, clathrin did not translocate to HCN1 and TRIP8b-containing puncta, suggesting that TRIP8b interacts with HCN and clathrin independently. We found TRIP8b present in the fraction of clathrin-coated vesicles purified from brain tissues. Stripping the clathrin coat proteins from the vesicles with Tris alkaline buffer resulted in concomitant release of TRIP8b. Our data suggest complex regulatory functions of TRIP8b in neuronal endocytosis through independent interaction with membrane proteins and components of the clathrin coat.
- (2011). Insulin receptor-related receptor as an extracellular alkali sensor. Cell Metab. 13 (6), 679–89 [+]
The insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH >7.9. The alkali-sensing property of IRR is conserved in frog, mouse, and human. IRR activation is specific, dose-dependent and quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess.
- (2010). Association of the subunits of the calcium-independent receptor of α-latrotoxin. Biochem. Biophys. Res. Commun. 402 (4), 658–62 [+]
CIRL-1 also called latrophilin 1 or CL belongs to the family of adhesion G protein-coupled receptors (GPCRs). As all members of adhesion GPCR family CIRL-1 consists of two heterologous subunits, extracellular hydrophilic p120 and heptahelical membrane protein p85. Both CIRL-1 subunits are encoded by one gene but as a result of intracellular proteolysis of precursor, mature receptor has two-subunit structure. It was also shown that a minor portion of the CIRL-1 receptor complexes dissociates, producing the soluble receptor ectodomain, and this dissociation is due to the second cleavage at the site between the site of primary proteolysis and the first transmembrane domain. Recently model of independent localization p120 and p85 on the cell surface was proposed. In this article we evaluated the amount of p120-p85 complex still presented on the cellular membrane and confirmed that on cell surface major amount of mature CIRL-1 presented as a p120-p85 subunit complex.
- (2010). Regulation of CIRL-1 proteolysis and trafficking. Biochimie 92 (4), 418–22 [+]
Calcium-independent receptor of alpha-latrotoxin (CIRL-1) is an adhesion G protein-coupled receptor implicated in the regulation of exocytosis. CIRL-1 biosynthesis involves constitutive proteolytic processing that takes place in the endoplasmic reticulum, requires the receptor's GPS domain, and yields heterologous two-subunit receptor complexes. It was proposed that the GPS-directed cleavage is based on cis-autoproteolysis. In this study, we demonstrate that activators of protein kinase C - PMA and ionomycin, can inhibit the cleavage of CIRL-1 precursor in transfected cells. Both reagents also downregulate trafficking of CIRL-1 to the cell surface that results in accumulation of the uncleaved receptor precursor inside the cells. Experiments with a non-cleavable soluble mutant of CIRL-1 showed that the downregulation of the receptor trafficking is independent of its cleavage. Our data suggest that the GPS proteolysis of CIRL-1 is not a purely autocatalytic process and may involve auxiliary proteins or factors that become available in the course of CIRL-1 trafficking.
- (2009). Dissociation of the subunits of the calcium-independent receptor of alpha-latrotoxin as a result of two-step proteolysis. Biochemistry 48 (14), 3230–8 [+]
CIRL (the calcium-independent receptor of alpha-latrotoxin), a neuronal cell surface receptor implicated in the regulation of exocytosis, is a member of the GPS family of chimeric cell adhesion/G protein-coupled receptors. The predominant form of CIRL is a membrane-bound complex of two subunits, p120 and p85. Extracellularly oriented p120 contains hydrophilic cell adhesion domains, whereas p85 is a heptahelical membrane protein. Both subunits are encoded by the same gene and represent products of intracellular proteolytic processing of the CIRL precursor. In this study, we demonstrate that a soluble form of CIRL also exists in vitro and in vivo. It results from the further cleavage of CIRL by a second protease. The site of the second cleavage is located in the short N-terminal extracellular tail of p85, between the GPS domain and the first transmembrane segment of CIRL. Thus, the soluble form of CIRL represents a complex of p120 noncovalently bound to a 15 amino acid residue N-terminal peptide fragment of p85. We have previously shown that mutations of CIRL in the GPS domain inhibit intracellular proteolytic processing and also result in the absence of the receptors from the cell surface. Our current data suggest that although CIRL trafficking to the cell membrane is impaired by mutations in the GPS region, it is not blocked completely. However, at the cell surface, the noncleaved mutants are preferentially targeted by the second protease that sheds the extracellular subunit. Therefore, the two-step proteolytic processing may represent a regulatory mechanism that controls cell surface expression of membrane-bound and soluble forms of CIRL.
- (2009). Novel GPS-containing G protein-coupled receptor from Monosiga brevicollis. Dokl. Biochem. Biophys. 427, 191–4
- (2009). Identification of proteins in complexes with alpha-latrotoxin receptors. Bioorg. Khim. 34 (6), 747–53 [+]
A thorough analysis of proteins capable of interacting with presynaptic receptors of alpha-latrotoxin was carried out. The protein components of receptor complexes were isolated from rat brain membranes by affinity chromatography on immobilized alpha-latrotoxin and antibodies to the cytoplasmic moiety of the calcium-independent receptor of alpha-latrotoxin (CIRL) followed by analysis by mass spectrometry. Several proteins were identified, with structural proteins, intracellular signal proteins, and proteins involved in the endocytosis and transport of synaptic vesicles being among them.
- (2008). Analysis of proteins interacting with TRIP8b adapter. Biochemistry Mosc. 73 (6), 644–51 [+]
Calcium-independent receptor of latrotoxin (CIRL) is an orphan heptahelical receptor implicated in regulation of exocytosis. To characterize molecular mechanisms of CIRL functioning, we searched for its intracellular partners using the yeast two-hybrid SR system with the cytoplasmic C-terminal fragment of CIRL as bait. One of the interacting proteins was identified as TRIP8b, a putative cytosolic adapter protein with multiple tetratricopeptide repeats. To understand functional significance of CIRL-TRIP8b interaction, we further isolated TRIP8b-interacting proteins by affinity chromatography of brain extracts on immobilized recombinant TRIP8b. Sixteen proteins were identified by mass spectrometry in the purified preparations. Clathrin and subunits of AP2 complex appeared to be the major TRIP8b-interacting proteins. Our data suggest a role of TRIP8b in receptor-mediated endocytosis.
- (2002). Post-translational proteolytic processing of the calcium-independent receptor of alpha-latrotoxin (CIRL), a natural chimera of the cell adhesion protein and the G protein-coupled receptor. Role of the G protein-coupled receptor proteolysis site (GPS) moti. J. Biol. Chem. 277 (48), 46518–26 [+]
The calcium-independent receptor of alpha-latrotoxin (CIRL), a neuronal cell surface receptor implicated in the regulation of exocytosis, is a natural chimera of the cell adhesion protein and the G protein-coupled receptor (GPCR). In contrast with canonic GPCRs, CIRL consists of two heterologous non-covalently bound subunits, p120 and p85, due to endogenous proteolytic processing of the receptor precursor in the endoplasmic reticulum. Extracellularly oriented p120 contains hydrophilic cell adhesion domains, whereas p85 resembles a generic GPCR. We determined that the site of the CIRL cleavage is located within a juxtamembrane Cys- and Trp-rich domain of the N-terminal extracellular region of CIRL. Mutations in this domain make CIRL resistant to the cleavage and impair its trafficking. Therefore, we have named it GPS for G protein-coupled receptor proteolysis site. The GPS motif is found in homologous adhesion GPCRs and thus defines a novel receptor family. We postulate that the proteolytic processing and two-subunit structure is a common characteristic feature in the family of GPS-containing adhesion GPCRs.
- (2002). Protein-tyrosine phosphatase-sigma is a novel member of the functional family of alpha-latrotoxin receptors. J. Biol. Chem. 277 (39), 35887–95 [+]
Receptor-like protein-tyrosine phosphatase sigma (PTPvarsigma) is essential for neuronal development and function. Here we report that PTPvarsigma is a target of alpha-latrotoxin, a strong stimulator of neuronal exocytosis. alpha-Latrotoxin binds to the cell adhesion-like extracellular region of PTPvarsigma. This binding results in the stimulation of exocytosis. The toxin-binding site is located in the C-terminal part of the PTPvarsigma ectodomain and includes two fibronectin type III repeats. The intracellular catalytic domains of PTPvarsigma are not required for the alpha-latrotoxin binding and secretory response triggered by the toxin in chromaffin cells. These features of PTPvarsigma resemble two other previously described alpha-latrotoxin receptors, neurexin and CIRL. Thus, alpha-latrotoxin represents an unusual example of the neurotoxin that has three independent, equally potent, and yet structurally distinct targets. The known structural and functional characteristics of PTPvarsigma, neurexin, and CIRL suggest that they define a functional family of neuronal membrane receptors with complementary or converging roles in presynaptic function via a mechanism that involves cell-to-cell and cell-to-matrix interaction.
- (1999). Structural requirements for alpha-latrotoxin binding and alpha-latrotoxin-stimulated secretion. A study with calcium-independent receptor of alpha-latrotoxin (CIRL) deletion mutants. J. Biol. Chem. 274 (6), 3590–6 [+]
Stimulation of neurotransmitter release by alpha-latrotoxin requires its binding to the calcium-independent receptor of alpha-latrotoxin (CIRL), an orphan neuronal G protein-coupled receptor. CIRL consists of two noncovalently bound subunits, p85, a heptahelical integral membrane protein, and p120, a large extracellular polypeptide with domains homologous to lectin, olfactomedin, mucin, the secretin receptor family, and a novel structural motif common for large orphan G protein-coupled receptors. The analysis of CIRL deletion mutants indicates that the high affinity alpha-latrotoxin-binding site is located within residues 467-891, which comprise the first transmembrane segment of p85 and the C-terminal half of p120. The N-terminal lectin, olfactomedin, and mucin domains of p120 are not required for the interaction with alpha-latrotoxin. Soluble p120 and all its fragments, which include the 467-770 residues, bind alpha-latrotoxin with low affinity suggesting the importance of membrane-embedded p85 for the stabilization of the complex of the toxin with p120. Two COOH-terminal deletion mutants of CIRL, one with the truncated cytoplasmic domain and the other with only one transmembrane segment left of seven, supported both alpha-latrotoxin-induced calcium uptake in HEK293 cells and alpha-latrotoxin-stimulated secretion when expressed in chromaffin cells, although with a different dose dependence than wild-type CIRL and its N-terminal deletion mutant. Thus the signaling domains of CIRL are not critically important for the stimulation of exocytosis in intact chromaffin cells by alpha-latrotoxin.
- (1997). alpha-Latrotoxin stimulates exocytosis by the interaction with a neuronal G-protein-coupled receptor. Neuron 18 (6), 925–37 [+]
alpha-Latrotoxin is a potent stimulator of neurosecretion. Its action requires extracellular binding to high affinity presynaptic receptors. Neurexin I alpha was previously described as a high affinity alpha-latrotoxin receptor that binds the toxin only in the presence of calcium ions. Therefore, the interaction of alpha-latrotoxin with neurexin I alpha cannot explain how alpha-latrotoxin stimulates neurotransmitter release in the absence of calcium. We describe molecular cloning and functional expression of the calcium-independent receptor of alpha-latrotoxin (CIRL), which is a second high affinity alpha-latrotoxin receptor that may be the major mediator of alpha-latrotoxin's effects. CIRL appears to be a novel orphan G-protein-coupled receptor, a member of the secretin receptor family. In contrast with other known serpentine receptors, CIRL has two subunits of the 120 and 85 kDa that are the result of endogenous proteolytic cleavage of a precursor polypeptide. CIRL is found in brain where it is enriched in the striatum and cortex. Expression of CIRL in chromaffin cells increases the sensitivity of the cells to the effects of alpha-latrotoxin, demonstrating that this protein is functional in coupling to secretion. Syntaxin, a component of the fusion complex, copurifies with CIRL on an alpha-latrotoxin affinity column and forms stable complexes with this receptor in vitro. Interaction of CIRL with a specific presynaptic neurotoxin and with a component of the docking-fusion machinery suggests its role in regulation of neurosecretion.
- (1996). Structure and evolution of neurexophilin. J. Neurosci. 16 (14), 4360–9 [+]
Using affinity chromatography on immobilized alpha-latrotoxin, we have purified a novel 29 kDa protein, neurexophilin, in a complex with neurexin l alpha. Cloning revealed that rat and bovine neurexophilins are composed of N-terminal signal peptides, nonconserved N-terminal domains (20% identity over 80 residues), and highly homologous C-terminal sequences (85% identity over 169 residues). Analysis of genomic clones from mice identified two distinct neurexophilin genes, one of which is more homologous to rat neurexophilin and the other to bovine neurexophilin. The first neurexophilin gene is expressed abundantly in adult rat and mouse brain, whereas no mRNA corresponding to the second gene was detected in rodents despite its abundant expression in bovine brain, suggesting that rodents and cattle primarily express distinct neurexophilin genes. RNA blots and in situ hybridizations revealed that neurexophilin is expressed in adult rat brain at high levels only in a scattered subpopulation of neurons that probably represent inhibitory interneurons; by contrast, neurexins are expressed in all neurons. Neurexophilin contains a signal sequence and is N-glycosylated at multiple sites, suggesting that it is secreted and binds to the extracellular domain of neurexin l alpha. This hypothesis was confirmed by binding recombinant neurexophilin to the extracellular domains of neurexin l alpha. Together our data suggest that neurexophilin constitutes a secreted glycoprotein that is synthesized in a subclass of neurons and may be a ligand for neurexins.
- (1992). Neurexins: synaptic cell surface proteins related to the alpha-latrotoxin receptor and laminin. Science 257 (5066), 50–6 [+]
A family of highly polymorphic neuronal cell surface proteins, the neurexins, has been identified. At least two genes for neurexins exist. Each gene uses alternative promoters and multiple variably spliced exons to potentially generate more than a 100 different neurexin transcripts. The neurexins were discovered by the identification of one member of the family as the receptor for alpha-latrotoxin. This toxin is a component of the venom from black widow spiders; it binds to presynaptic nerve terminals and triggers massive neurotransmitter release. Neurexins contain single transmembrane regions and extracellular domains with repeated sequences similar to sequences in laminin A, slit, and agrin, proteins that have been implicated in axon guidance and synaptogenesis. An antibody to neurexin I showed highly concentrated immunoreactivity at the synapse. The polymorphic structure of the neurexins, their neural localization, and their sequence similarity to proteins associated with neurogenesis suggest a function as cell recognition molecules in the nerve terminal.
- (1992). Synaptotagmin: a calcium sensor on the synaptic vesicle surface. Science 256 (5059), 1021–5 [+]
Neurons release neurotransmitters by calcium-dependent exocytosis of synaptic vesicles. However, the molecular steps transducing the calcium signal into membrane fusion are still an enigma. It is reported here that synaptotagmin, a highly conserved synaptic vesicle protein, binds calcium at physiological concentrations in a complex with negatively charged phospholipids. This binding is specific for calcium and involves the cytoplasmic domain of synaptotagmin. Calcium binding is dependent on the intact oligomeric structure of synaptotagmin (it is abolished by proteolytic cleavage at a single site). These results suggest that synaptotagmin acts as a cooperative calcium receptor in exocytosis.
- (1991). Binding of synaptotagmin to the alpha-latrotoxin receptor implicates both in synaptic vesicle exocytosis. Nature 353 (6339), 65–8 [+]
A vertebrate neurotoxin, alpha-latrotoxin, from black widow spider venom causes synaptic vesicle exocytosis and neurotransmitter release from presynaptic nerve terminals. Although the mechanism of action of alpha-latrotoxin is not known, it does require binding of alpha-latrotoxin to a high-affinity receptor on the presynaptic plasma membrane. The alpha-latrotoxin receptor seems to be exclusively at the presynaptic plasmamembrane. Here we report that the alpha-latrotoxin receptor specifically binds to a synaptic vesicle protein, synaptotagmin, and modulates its phosphorylation. Synaptotagmin is a synaptic vesicle-specific membrane protein that binds negatively charged phospholipids and contains two copies of a putative Ca(2+)-binding domain from protein kinase C (the C2-domain), suggesting a regulatory role in synaptic vesicle fusion. Our findings suggest that a physiological role of the alpha-latrotoxin receptor may be the docking of synaptic vesicles at the active zone. The direct interaction of the alpha-latrotoxin receptor with a synaptic vesicle protein also suggests a mechanism of action for this toxin in causing neurotransmitter release.
- (1990). Isolation and properties of the alpha-latrotoxin receptor. EMBO J. 9 (6), 2023–7 [+]
The receptor protein of alpha-latrotoxin (alpha LTx, a neurotoxin with 'pure' presynaptic action isolated from black widow spider venom), was solubilized by Triton X-100 from bovine brain membranes and purified by affinity chromatography on alpha LTx-Sepharose. The purified receptor preparation contained four major polypeptides of molecular masses 200 (alpha), 160 (alpha'), 79 (beta) and 43 (gamma) kd according to SDS electrophoresis with molecular ratio alpha 1 alpha' 1 beta 2 gamma 2. The alpha- and alpha'-subunits are glycoproteins binding to wheat germ lectin and can be separated under non-denaturing conditions by anion exchange chromatography. Purified to homogeneity, both of them, though differing in the carbohydrate composition, retain the alpha LTx-binding activity and give closely related peptide maps. Anti-alpha antibodies recognize the alpha'-subunit as well. These results suggest that alpha LTx receptor is present in purified preparations in two very close forms containing the alpha- or alpha'-subunit. Beta and gamma proteins do not specifically bind alpha LTx and their physiological role is unclear. They form a complex with solubilized alpha- and alpha'-subunits independently of alpha LTx presence. The receptor proteins were purified to homogeneity by high performance gel filtration in the presence of SDS, their amino acid composition was determined.