Severe Impairment of Leukocyte Recruitment in ppGalNAcT-1-Deficient Mice

P-selectin glycoprotein ligand-1 plays an important role in leukocyte recruitment. Its binding affinity to selectins is modulated by posttranslational modifications. The polypeptide N-acetylgalactosamine transferase-1 (ppGalNAcT-1) initiates core-type protein O-glycosylation. To address whether the glycosylation of P-selectin glycoprotein ligand-1 by ppGalNAcT-1 is important for leukocyte recruitment in vivo, we investigated leukocyte recruitment in untreated and TNF-alpha-treated cremaster muscles comparing ppGalNAcT-1 deficient mice (Galnt1(-/-)) and wild-type mice. In untreated and TNF-alpha-treated Galnt1(-/-) mice, leukocyte rolling, adhesion, and transmigration were significantly reduced, with markedly increased rolling velocity compared with control mice. L-selectin dependent leukocyte rolling was completely abolished in Galnt1(-/-) mice compared with wild-type mice. Thioglycollate-induced peritonitis experiments with chimeric mice revealed that hematopoietic ppGalNAcT-1 is important for leukocyte recruitment. These data show that the loss of ppGalNAcT-1 led to reduced leukocyte rolling and recruitment and increased rolling velocity, suggesting a predominant role for ppGalNAcT-1 in attaching functionally relevant O-linked glycans to selectin ligands. The Journal of Immunology, 2012, 188: 5674-5681.