Differential expression of five sialyltransferase genes in human tissues.

H Kitagawa,J.C Paulson

doi:10.1016/s0021-9258(17)32390-6

Abstract

Cell type-specific expression of specific carbohydrate structures on cell surface glycoproteins and glycolipids is increasingly recognized for providing information relevant to cell-cell interactions in developing and adult organisms. Sialyltransferases contribute to the diversity in carbohydrate structure through their attachment of sialic acid in various terminal positions on glycolipid and on glycoprotein (N-linked and O-linked) carbohydrate groups. In this report, differential expression of five sialyltransferase genes in human tissues is evaluated as a potential mechanism to account for cell type-specific variation in terminal sialoside structures produced by a cell. For this analysis, the complete cDNA of the human Gal beta 1,3GalNAc alpha 2,3-sialyltransferase and a partial cDNA of the developmentally regulated STX gene were cloned. Northern analysis was performed using these cDNAs and those of three previously cloned human sialyltransferase genes as probes. Each of the five sialyltransferase genes exhibits dramatic differential expression in the 16 adult and 5 fetal human tissues examined, and expression of each gene appears to be independently regulated. Comparison with fragmentary earlier studies of the expression of several of the same enzymes in rat tissues suggests that the overall pattern of expression is largely conserved.

Highlights

Cell type-specific expression of specific carbohydrate The leukocyte glycoproteinCD22, a member of the imstructures on cell surface glycoproteins and glycolipids munoglobulin superfamily of integral membrane proteins, is is increasinglyrecognizedforprovidinginformation thought t o participate in B-cell/B-celland B-cellPT-celladhesion relevant to cell-cell interactions in developing and ad(uStlatmenkovicet al., 1991; Wilsonet al., 1991)and has been organisms
Each of thefive lation of polysialylation may be important as a mechanism for sialyltransferasegenesexhibitsdramaticdifferential maintaining NCAM in its low adhesion form during the cell expression in the 16 adult and 5 fetal human tissues migrations involved in thedevelopment of the nervous system examined, and expression of each gene appears to be (Rutishauser et al, 1988;Livingstonet al., 1990).The polysialic independently regulated
Sialic acid containing carbohydrate groups of glycoproteins structures areexpressed in a tissue- and cell type-specificmanand glycolipids have been shown to function in biological proc- ner, implies that theterminal sialylation of cell surface carboesses ranging from intracellular t r a ~ c k i n gto cell differentia- hydrate groups is regulated

Summary

RESULTS

As judged by homology with the ratsequence (Livingstonand Paulson, 1993). Cloning of the Human ST30 Sialy~trunsfe~usecDNA-Randomprimed human placenta cDNA was ligated with EcoRI linkers, . The compIete cedingsequencesofthe two types of hST30 cDNA were contained in the cDNA inserts of hST3O-1 (long) and hST30-2 (short), which each coded for identical protein sequences. The differences in the human protein include a single amino acid deletion in the c~oplasmtiacil and a two-a~inoacid deletion in thestem region. The longest of the two cDNAs has anextremely long (930-bpf fi'-untransIated region which contains muItipIe upstream ATG codons and upstreamopen reading frames ("minicistrons"). There are 16 ATG codons upstream from the putaof human ST30 which lacked the first 44 amino acids of the open tive tran~lationinitiation site. The cDNA containing the resulting fusion protein was excised fromthe pGIR construct and inserted into the S a l - S m a l sites of the expression vector pSVL to yield the expression plasmid 130HP. Expression of the SolubleForm of the Siulyltra~ferusaend Assaying combinant soluble form of the human ST30 fusion protein was Enzyme Activity-The expression plasmid (10 pg) was transfected into generated by replacing the first 44 amino acids o f the sialyl-

91 A l aL e uL e uG l uA s pA s p

61 GAG ATT GAC GCCAC AGC TTCGTC ATC AGG TGC AAC CTGCC CCA GTA CAG GAG TATGCC

Findings

DISCUSSION