The P1 histo‐blood group antigen is present on human red blood cell glycoproteins

Abstract

BACKGROUND The P1 antigen was first described in 1927 and belongs to the P1PK histo‐blood group system, together with Pk and NOR. The A4GALT‐encoded 4‐α‐galactosyltransferase synthesizes these antigens and has been considered to extend glycolipids exclusively. However, contradicting studies have been published regarding the presence of P1 on human glycoproteins. In other species, P1 occurs on glycoproteins. Furthermore, human ABH antigens occur on both glycolipids and glycoproteins and are biochemically related to P1. Thus, we hypothesized that P1 is present on RBC glycoproteins in humans. STUDY DESIGN AND METHODS RBCs of known P1/P2 status (phenotype and rs8138197 genotype) were used. The RBC surface glycans were modified with α‐galactosidases, papain, and/or peptide‐N‐glycosidase F. RBC membrane proteins were analyzed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis/immunoblot. A new P 1/P 2‐allelic discrimination assay based on rs5751348 was validated. RESULTS P1 occurs on various glycoproteins, seen as smearlike patterns in anti‐P1‐stained immunoblots with RBC membranes of P1 but not P2 or p phenotype. There was a significant difference between the staining of P 1‐homozygous and P 1‐heterozygous RBCs (P 1P 1 > P 1P 2), as well as intragenotypic variation. Immunoblotting banding patterns show major carriers at approximately 50 and 100 kDa. P1 staining was lost after treatment of RBCs with α‐galactosidase of broad Galα‐1,3/4/6‐specificity. Peptide‐N‐glycosidase F treatment reduced the P1 signal, while papain or α‐1,3‐specific galactosidase did not. P 1/P 2 status was confirmed by a new rs5751348 assay. CONCLUSION Our data indicate that the P1 antigen can reside on human RBC glycoproteins. Glycosidase studies suggest that at least part of the epitopes occur on N‐glycans.

Blood group P1 antigen–bearing glycoproteins are functional but less efficient receptors of Shiga toxin than conventional glycolipid-based receptors

“…P1 antigens on glycoproteins are known to bind STx, and column coupling with P1-containing proteins has been used to purify STx (25,26,33). P1 antigens on glycoproteins are infrequently observed in mammalian cells, although erythrocytes are likely to express them (34). In this study, hA4GalT synthesized a small amount of P1 antigens on glycoproteins only when overexpressed (Fig.…”

Blood group P1 prediction using multiplex PCR genotyping of A4GALT among Thai blood donors

“…Therefore, rs5751348 should be used as the genetic determinant to predict P1 antigen expression 22 . In a recent study, a new P 1 / P 2 ‐allelic discrimination assay based on rs5751348 was validated, and the results were confirmed to be correlated to the P 1 / P 2 status 36 …”

Human Gb3/CD77 synthase produces P1 glycotope-capped N-glycans, which mediate Shiga toxin 1 but not Shiga toxin 2 cell entry

“…Since then, there was a general agreement that GSLs are the only carriers of the P1 glycotope. Recently (39), suggested that some human erythrocytes of P 1 phenotype display P1 not just on GSLs, but also on glycoproteins, and implicated GLUT1 and Band 3 as likely major carriers of the P1 glycotope. However, the evidence was limited to western blotting results.…”