Localization of α1,3-fucosyltransferase VI in Weibel-Palade bodies of human endothelial cells

Surface glycosylation of endothelial cells is relevant to various processes including coagulation, inflammation, metastasis. and lymphocyte homing. One of the essential sugars involved in these processes is fucose linked alpha 1-->3 to N-acetylglucosamine. A family of alpha 1,3-fucosyltransterases (FucTs) called FucT-III. IV, V, VI, VII, and IX is able to catalyze such fucosylations. Reverse transcription-PCR analysis revealed that human umbilical vein endothelial cells express all of the FucTs except FucT-IX. The predominant activity, as inferred by acceptor specificity of enzyme activity in cell lysates. is compatible with the presence of FucT-VI. By using an antibody to recombinant soluble FucT-VI. the enzyme colocalized with beta 4-galactosyltransterase-1 to the Golgi apparatus. By using a polyclonal antiserum raised aga inst a 17-aa peptide of the variable (stem) region of the FucT-VI. immunocytochemical staining of FucT-VI was restricted to Weibel-Palade bodies, as determined by colocalization with beta-selectin and von Willebrand factor. SDS/PAGE immunoblotting and amino acid sequencing of internal peptides confirmed the identity of the antigen isolated by the peptide-specific antibody as FucT-VI. Storage of a fucosyltransferase in Weibel-Palade bodies suggests a function independent of Golgi-associated glycosylation.