Role for hepatic and circulatory ST6Gal-1 sialyltransferase in regulating myelopoiesis.
Recent findings have established a role for the ST6Gal-1 sialyltransferase in modulating inflammatory cell production during Th1 and Th2 responses. ST6Gal-1 synthesizes the Sia(alpha2,6) to Gal(beta1,4)GlcNAc linkage on glycoproteins on cell surfaces and in systemic circulation. Engagement of P1, one of six promoter/regulatory regions driving murine ST6Gal-1 gene expression, generates the ST6Gal-1 for myelopoietic regulation. P1 utilization, however, is restricted to the liver and silent in hematopoietic cells. We considered the possibility that myelopoiesis is responsive to the sialylation of liver-derived circulatory glycoproteins, such that reduced alpha2,6-sialylation results in elevated myelopoiesis. However, 2-dimensional differential in gel electrophoresis (2D-DIGE) analysis disclosed only minimal alterations in the sialylation of sera glycoproteins of ST6Gal-1-deficient mice when compared with wild-type controls, either at baseline or during an acute phase response when the demand for sialylation is greatest. Furthermore, sera from ST6Gal-1-deficient animals did not enhance myelopoietic activity in ex vivo colony formation assays. Whereas there was only minimal consequence to the alpha2,6-sialylation of circulatory glycoproteins, ablation of the P1 promoter did result in strikingly depressed levels of ST6Gal-1 released into systemic circulation. Therefore, we considered the alternative possibility that myelopoiesis may be regulated not by the hepatic sialyl glycoproteins, but by the ST6Gal-1 that was released directly into circulation. Supporting this, ex vivo colony formation was notably attenuated upon introduction of physiologic levels of ST6Gal-1 into the culture medium. Our data support the idea that circulatory ST6Gal-1, mostly of hepatic origin, limits myelopoiesis by a mechanism independent of hepatic sialylation of serum glycoproteins.
Jones
Mark B
MB
Departments of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
Nasirikenari
Mehrab
M
Feng
Li
L
Migliore
Marina T
MT
Choi
Kyoung-Soo
KS
Kazim
Latif
L
Lau
Joseph T Y
JT
D000818:Animals; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000737:chemistry; D006031:Glycosylation; D006412:Hematopoietic Stem Cells / Q000166:cytology; D008099:Liver / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D038042:Myelopoiesis; D012799:Sialyltransferases / Q000097:blood* / Q000378:metabolism*; D013234:Stem Cells; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D006023:Glycoproteins; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase