Localization of alpha 1,3-fucosyltransferase VI in Weibel-Palade bodies ofhuman endothelial cells

Surface glycosylation of endothelial cells is relevant to various processes including coagulation, inflammation, metastasis. and lymphocyte homing. On e of the essential sugars involved in these processes is fucose linked alph a 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 fuc osylations. Reverse transcription-PCR analysis revealed that human umbilica l vein endothelial cells express all of the FucTs except FucT-IX. The predo minant activity, as inferred by acceptor specificity of enzyme activity in cell lysates. is compatible with the presence of FucT-VI. By using an antib ody to recombinant soluble FucT-VI. the enzyme colocalized with beta 4-gala ctosyltransterase-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 Willebra nd factor. SDS/PAGE immunoblotting and amino acid sequencing of internal pe ptides confirmed the identity of the antigen isolated by the peptide-specif ic antibody as FucT-VI. Storage of a fucosyltransferase in Weibel-Palade bo dies suggests a function independent of Golgi-associated glycosylation.