Alexey V. Pshezhetsky

Accredited Professor

Contact Information

CHU Sainte-Justine
Département de pédiatrie
3175, chemin Côte-Ste-Catherine
Montréal (Québec)
H3T 1C5

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T 514 345-4931, poste 2736
F 514 345-4766
alexei.pchejetski@umontreal.ca

Themes

Lysosomal biology and lysosomal storage diseases

Lysosomes are cytoplasmic organelles harbouring over 100 hydrolytic enzymes involved in the degradation of essentially all types of biological macromolecules.  Any failure in the biogenesis, lysosomal targeting, supramolecular organization or function of one or more lysosomal enzymes can result in the progressive metabolic diseases called lysosomal storage diseases because of the massive accumulation of the undegraded substrates of the deficient enzymes in the lysosomes of the affected tissues.  Our research aims at discovering the genes mutated in lysosomal diseases, identifying the molecular and biochemical defects in patients and developing therapies with a special emphasis on diseases caused by the deficiencies of lysosomal sialidases (sialidosis, galactosialidosis) and N-acetyltransferases (mucopolysaccharidosis IIIC).

Sialic acids and sialidases in cell signalling

Sialic acids are abundantly expressed on the cell surface and implicated in mediating recognition between the cells, between the cells and extracellular matrix as well as between the cells and a range of pathogenic viruses, bacteria and protozoa during the inflammatory and immune reactions.  Much less is known about the role of sialidases (also called neuraminidases) and sialotransferases that can regulate cellular affinity by modifying the sialylation of cell surface molecules.  Using the genetically targeted mouse models we study the role of neuraminidase 1 (Neu1) in signalling during the immune response, phagocytosis and glucose uptake, as well as the role of neuraminidase 4 (Neu4) in brain development.

Serine carboxypeptidases in regulation of vasoconstriction and elastogenesis

Short vasoactive peptides are recognized as potent regulators of blood circulation.  Through their interaction with different cell surface receptors peptides can modulate blood pressure by such diverse mechanisms as contracting vascular smooth muscles, increasing or decreasing plasma volume, or by induction or suppression of vascular wall remodelling.  Therefore proteases involved in the catabolic proteolysis of circulating vasoactive peptides, which regulates their functional longevity and availability play important role in regulation of vascular resistance.  Using the knock-out mouse model we study the input of the major lysosomal serine carboxypeptidase A (cathepsin A) in post-translational processing of vasoactive peptides including angiotensin and endothelin.

Functional proteomics and phosphoproteomics

Phosphorylation is the most frequent and important post-translational modification of proteins.  Despite intensive research dedicated to development of methods for the analysis of a phosphoproteome, identification of low-abundant cellular phosphoproteins still remains challenging, highlighting the need for novel techniques. Our team is involved in development of new technologies for the global analysis and quantitative analysis of a phosphoproteome based on affinity resins for isolation of phosphopeptides and phosphoproteins and isotopic peptide tags. This technology should allow comparison of phosphoproteomes tracing up- and down-regulation of the individual proteins in order to identify novel drug targets and pharmacologically relevant metabolic and signaling pathways.

Publications

  • Pshezhetsky, A.V., Richard, C., Michaud, L., Igdoura, S., Wang, S., Elsliger, M.A., Qu, J., Leclerc, D., Gravel, R., Dallaire, L. and Potier, M. : Human lysosomal sialidase : cloning expression, chromosomal mapping and characterization of mutations in sialidosis patients. Nature Genetics, 1997; 15, 316-320.
  • Taurin S,Seyrantepe V, Orlov SN, Trembley TL, Bennett MR, Hamet P, Pshezhetsky AV. Proteome analysis and functional expression identify mortalin as an antiapoptotic gene induced by elevation of [Na+]i/[K+]i ratio in cultured vascular smooth muscle cells. Circ Res, 2002 Nov 15;91(10):915-22.
  • Raymond M-A, Désormeaux A, Laplante P, Vigneault N, Filep JG, Landry K, Pshezhetsky AV, Hébert M-J.  Apoptosis of endothelial cells triggers a caspase-dependent anti-apoptotic paracrine loop active on VSMC.  FASEB J, 2004;18(6):705-707.
  • Hřebíček M, Mrázová L, Seyrantepe V, Durand S, Roslin NM, Nosková L, Hartmannová H, Ivánek R, Čížková A, Poupětová H, Sikora J, Uřinovská J, Stránecký V, Zeman J, Lepage P, Roquis D, Verner A, Ausseil J, Beesley CE, Maire I, Poorthuis BJ, van de Kamp J, van Diggelen OP, Wevers RA, Hudson TJ, Fujiwara TM, Majewski J, Morgan K, Kmoch S, Pshezhetsky AV.  Mutations in TMEM76 cause mucopolysaccharidosis IIIC (Sanfilippo C syndrome). Am J Hum Genet, 2006;79(5) :807-819.
  • Liang F, Seyrantepe V, Landry K, Ahmad R, Ahmad A, Stamatos NM, Pshezhetsky AV. Monocyte differentiation up-regulates the expression of the lysosomal sialidase, Neu1 and triggers its targeting to the plasma membrane via major histocompatibility complex class (MHC) class II-positive compartments.  J Biol Chem, 2006; 281(37):27526-27538.
  • Pshezhetsky AV, Fedjaev M, Ashmarina L, Mazur A, Budman L, Sinnett D, Labuda D, Beaulieu J-F, Ménard D, Nifant’ev I, Levy É,.  Subcellular proteomics of cell differentiation: quantitative analysis of the plasma membrane proteome of Caco-2 cells.  Proteomics, 2007 ; 7(13):2201-2215.
  • Seyrantepe V, Canuel M, Zeng J, Landry K, Liang F, Durand S, Carpentier S, Gravel RA, Michaud J, Marchesini S, Zwingmann C, Morales CR, Levade T, Pshezhetsky AV.  Mice deficient in the Neu4 sialidase exhibit abnormal ganglioside catabolism and lysosomal storage. Hum Mol Genet, 2008, 17(11):1556-1568.
  • Seyrantepe V, Peng J, Ernest S, Fedjaev M, Kadota Y, Canuel M, Zeng J, Morales CR, Itoh K, Hinek A, Tremblay J, Pshezhetsky AV.  Enzymatic activity of lysosomal carboxypeptidase (cathepsin) A is required for proper elastic fiber formation and inactivation of endothelin-1. Circulation, 2008, 117(15):1973-81.