tailieunhanh - Báo cáo khoa học: Differential expression of endogenous sialidases of human monocytes during cellular differentiation into macrophages

Sialidases are enzymes that influence cellular activity by removing terminal sialic acid from glycolipids and glycoproteins. Four genetically distinct sia-lidases have been identified in mammalian cells. In this study, we demon-strate that three of these sialidases, lysosomal Neu1 and Neu4 and plasma membrane-associated Neu3, are expressed in human monocytes. When measured using the artificial substrate 2¢-(4-methylumbelliferyl)-a-d-N-acetylneuraminic acid (4-MU-NANA), sialidase activity of monocytes increased up to 14-fold per milligram of total protein after cells had differ-entiated into macrophages. . | ềFEBS Journal Differential expression of endogenous sialidases of human monocytes during cellular differentiation into macrophages Nicholas M. Stamatos1 2 Feng Liang3 Xinli Nan1 Karine Landry3 Alan S. Cross2 Lai-Xi Wang1 and Alexey V. Pshezhetsky3 1 Institute of Human Virology University of Maryland Baltimore MD USA 2 Division of Infectious Diseases Department of Medicine University of Maryland MedicalCenter Baltimore MD USA 3 HopitalSainte-Justine and Departement de Pediatrie Universite de Montreal Montreal Quebec Canada Keywords differentiation glycoconjugates human monocytes sialidases sialic acid Correspondence N. M. Stamatos 725 West Lombard St. Institute of Human Virology University of Maryland MedicalSystem Baltimore MD 21201 USA Fax 1 410 7064619 Tel 1 410 7062645 E-mail stamatos@ Received 20 October 2004 revised 11 March 2005 accepted 22 March 2005 doi Sialidases are enzymes that influence cellular activity by removing terminal sialic acid from glycolipids and glycoproteins. Four genetically distinct sia-lidases have been identified in mammalian cells. In this study we demonstrate that three of these sialidases lysosomal Neu1 and Neu4 and plasma membrane-associated Neu3 are expressed in human monocytes. When measured using the artificial substrate 2 - 4-methylumbelliferyl -a-D-N-acetylneuraminic acid 4-MU-NANA sialidase activity of monocytes increased up to 14-fold per milligram of total protein after cells had differentiated into macrophages. In these same cells the specific activity of other cellular proteins . b-galactosidase cathepsin A and alkaline phosphatase increased only two- to fourfold during differentiation of monocytes. Sialidase activity measured with 4-MU-NANA resulted from increased expression of Neu1 as removal of Neu1 from the cell lysate by immunoprecipitation eliminated more than 99 of detectable sialidase activity. When exogenous mixed bovine gangliosides were used as substrates there was