Evgeny Kanshin

Publications (2)9.2 Total impact

• Article: Regulation of phagocytosis in macrophages by neuraminidase 1.

  Volkan Seyrantepe, Alexandre Iannello, Feng Liang, Evgeny Kanshin, Preethi Jayanth, Suzanne Samarani, Myron R Szewczuk, Ali Ahmad, Alexey V Pshezhetsky
  [show abstract] [hide abstract]
  ABSTRACT: The differentiation of monocytes into macrophages and dendritic cells is accompanied by induction of cell-surface neuraminidase 1 (Neu1) and cathepsin A (CathA), the latter forming a complex with and activating Neu1. To clarify the biological importance of this phenomenon we have developed the gene-targeted mouse models of a CathA deficiency (CathA(S190A)) and a double CathA/Neu1 deficiency (CathA(S190A-Neo)). Macrophages of CathA(S190A-Neo) mice and their immature dendritic cells showed a significantly reduced capacity to engulf Gram-positive and Gram-negative bacteria and positively and negatively charged polymer beads as well as IgG-opsonized beads and erythrocytes. Properties of the cells derived from CathA(S190A) mice were indistinguishable from those of wild-type controls, suggesting that the absence of Neu1, which results in the increased sialylation of the cell surface proteins, probably affects multiple receptors for phagocytosis. Indeed, treatment of the cells with purified mouse Neu1 reduced surface sialylation and restored phagocytosis. Because Neu1-deficient cells showed reduced internalization of IgG-opsonized sheep erythrocytes whereas binding of the erythrocytes to the cells at 4 degrees C persisted, we speculate that the absence of Neu1 in particular affected transduction of signals from the Fc receptors for immunoglobulin G (FcgammaR). Indeed the macrophages from the Neu1-deficient mice showed increased sialylation and impaired phosphorylation of FcgammaR as well as markedly reduced phosphorylation of Syk kinase in response to treatment with IgG-opsonized beads. Altogether our data suggest that the cell surface Neu1 activates the phagocytosis in macrophages and dendritic cells through desialylation of surface receptors, thus, contributing to their functional integrity.
  Journal of Biological Chemistry 11/2009; 285(1):206-15. · 4.77 Impact Factor
• Article: The stoichiometry of protein phosphorylation in adipocyte lipid droplets: analysis by N-terminal isotope tagging and enzymatic dephosphorylation.

  Evgeny Kanshin, Shupei Wang, Lyudmila Ashmarina, Michael Fedjaev, Ilya Nifant'ev, Grant A Mitchell, Alexey V Pshezhetsky
  [show abstract] [hide abstract]
  ABSTRACT: Most phosphoproteomic studies to date have been limited to the identification of phosphoproteins and their phosphorylation sites, and have not assessed the stoichiometry of protein phosphorylation, a critical parameter reflecting the dynamic equilibrium between phosphorylated and non-phosphorylated pools of proteins. Here, we used a method for measuring phosphorylation stoichiometry through isotope tagging and enzymatic dephosphorylation of tryptic peptides. Using this method, protein digests are divided into two equal aliquots that are modified with either light or heavy isotope tags. One aliquot is dephosphorylated by alkaline phosphatase. Finally, the peptide mixtures are recombined and LC-MS/MS analysis is performed. With this method, we studied adipocytes of mice stimulated with CL316,243, a beta-3 adrenergic agonist known to induce lipolysis and marked phosphorylation changes in proteins of the lipid droplet surface. In lipid droplet preparations, CL316,243 administration increased phosphorylation of proteins related to regulation of signaling, metabolism and intracellular trafficking in white adipose tissue, including hormone-sensitive lipase which was 80% phosphorylated at the previously reported site, Ser-559, and the lipid surface protein perilipin, which was phosphorylated by approximately 60 and approximately 40% at previously unreported sites, Ser-410 and Ser-460.
  Proteomics 11/2009; 9(22):5067-77. · 4.43 Impact Factor