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Glycoproteomic and phenotypic elucidation of B4GALNT2 expression variants in the SID histo-blood group system

ABSTRACT: The Sda histo-blood group antigen [GalNAcβ1-4(NeuAcα2-3)Galβ-R] is present in colon, kidney and body fluids among 96-98% of Europeans whilst 90% have Sda-positive erythrocytes. Sda is implicated in various infections and constitutes a potential biomarker for colon cancer. The 2-4% truly Sd(a‒) individuals may produce anti-Sda, which can lead to incompatible blood transfusions, especially if donors with the high-expressing Sda phenotype, Sd(a++) or Cad, are involved. It was hypothesized that defects in the B4GALNT2-encoded β4GalNAc-T2 glycosyltransferase underlies the null phenotype. We recently reported the association of B4GALNT2 mutations with the Sd(a‒) phenotype, which formally established the SID blood-group system. In the present study, we provide causal proof and glycoprotein profiling underpinning this correlation. Phenotypically Sd(a‒) HEK293 cells were transfected with different B4GALNT2 constructs and evaluated by immunostaining and LC-MS/MS-based glycoproteomics. The pre¬dominant SIDnull allele with SNP rs7224888:T>C (p.Cys406Arg) abolished Sda synthesis, while this antigen was detectable as N- or O-glycans on multiple glycoproteins following transfection of wildtype B4GALNT2. Surprisingly, two rare missense SNPs, rs148441237:A>G and rs61743617:C>T, found in a Sd(a‒) compound heterozygote gave results similar to wildtype. To elucidate if Sd(a++)/Cad is also due to B4GALNT2 alterations, its coding region and 2 kbp upstream were sequenced in five Cad individuals. No genetic changes were associated with this phenotype but a detailed erythroid Cad glycoprotein profile was obtained, especially for GLPA (O-glycosylation) and, for the first time, B3AT (N-glycosylation). In conclusion, the p.Cys406Arg β4GalNAc-T2 variant causes Sda-deficiency in humans, while the enigmatic Cad phenotype remains unresolved, albeit further characterized.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Hepatocyte, Cell Culture, Blood

SUBMITTER: Jonas Nilsson

LAB HEAD: Martin L Olsson

PROVIDER: PXD023943 | Pride | 2022-04-07

REPOSITORIES: Pride

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			Action	DRS
	Byonic_hits_HEK293_N-glycopeptides.xlsx	Xlsx
	Byonic_hits_HEK293_O-glycopeptides.xlsx	Xlsx
	Byonic_hits_RBC_N-glycopeptides.xlsx	Xlsx
	Byonic_hits_RBC_O-glycopeptides.xlsx	Xlsx
	Lumos_190916_56.raw	Raw

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Project description:A screening process was used to determine the aciduric capacities of a diverse set of Listeria monocytogenes strains and was based on the capacity to grow at pH 5.0 in the presence 4 different organic acids. Food and clinical isolates tended to be more resistant but strain genetic groupings were found to be only weakly linked to sodium diacetate (SDA)-resistance. Representative and comparatively aciduric food isolates FW04/0023 and FW04/0025 were found to accumulate reduced levels of acetate anion and K+ ion during growth in the presence of SDA, compared to more acid sensitive reference strains EGD (ATCC BAA-739) and ATCC 19111. The aciduric nature of FW04/0023 and FW04/0025 was also reflected by their comparatively high tolerance to pH 2.4 acid challenge; a property boosted by the presence of SDA, and growth-phase dependent acid tolerance. Transcriptomic analyses revealed increased levels of SDA did not activate or promulgate the response of any of the known acid protective mechanisms, except for acetoin biosynthesis. Elevated levels of unprotonated SDA (20 mM SDA at pH 5.0) was found to have broad effects on gene expression that could be differentiated from effects caused by mildly acidic conditions (pH 5.0) and substantial strain variation was also found. Collated SDA mainly effect genes associated with virulence, cell wall processes, DNA repair, and cofactor and lipid biosynthesis. Strain FW04/0025 was more responsive to elevated unprotonated SDA increasing the expression of 222 genes (>2-fold change, p<0.05), compared to 112 genes for strain EGD. Key differences between the strains in relation to SDA-enhanced transcript abundance in FW04/0023 were primarily associated with the cell wall, oxidative stress management, intermediary metabolism, and several hypothetical proteins. This complement of different responses could potentially alter phenotypes resulting in different cell envelope properties and metabolic properties that effect accumulation of acetate anion. The data demonstrates that amongst different L. monocytogenes strains acetate has differing effects that may ultimately influence growth efficiency under stressful conditions relevant to acidic foods and the gastrointestinal environment. The microarray component of the experiments had the aim of determining: i) To examine the affect of elevated levels of unprotonated sodium diacetate (21 mM sodium diacetate added to cultures at pH 5.0, resulting in ~7.7 mM unprotonated acetate) compared to mild acid stress at pH 5.0 in which lower levels of acetate accumulates through natural end-product formation. ii) To examine the gene expression responses of two L. monocytogenes strains that had different intrinsic acid resistances, including an organic acid resistant strain FW04/0025 and a more sensitive reference strain EGD on which genome the microarray oligonucleotide set is based.

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Glycoproteomic and phenotypic elucidation of B4GALNT2 expression variants in the SID histo-blood group system

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