Identification of an endogenous inhibitor of the UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyl transferase as apolipoprotein A1.
A previously described inhibitor of the UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyltransferase (GalNAc-T) (Quiroga et al., 1, 2), was purified from chicken blood serum by a new procedure. When subjected to SDS-PAGE, two major polypeptides of 27 and 70 kDa were observed. When tested in vitro, only the 27 kDa polypeptide inhibited the GalNAc-T. When added to chick cerebral embryonic neurons in culture, both polypeptides inhibited neuritogenesis. Both the 27 kDa and the 70 kDa fractions were present in the cells at 3 h following their addition to the cultures; both polypeptides had aneuritogenic activity and both inhibited the incorporation of [3H]-galactose into the cell gangliosides modifying their labeling pattern to a similar extent. Sequencing of the amino terminal end of the polypeptides showed that 18 and 9 amino acids from, respectively, the 27 and the 70 kDa polypeptides, were 100% homologues with the corresponding region of chick apolipoprotein Al (apo Al). After addition to cells in culture, no interconversion between the two polypeptides was detected after up to 20 h in culture. A monoclonal antibody that recognizes only the 70 kDa polypeptide, blocks its aneuritogenic effect without modifying that of the 27 kDa fraction. It is concluded that the endogenous inhibitor of GalNAc-T is apo Al.
Conde
C B
CB
Centro de Investigaciones en Química Biológica de Córdoba, CI-QUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
Grabois
V R
VR
Deza
S N
SN
Caputto
B L
BL
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D016632:Apolipoprotein A-I / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D001921:Brain / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D004591:Electrophoresis, Polyacrylamide Gel; D005690:Galactose / Q000378:metabolism; D005732:Gangliosides / Q000096:biosynthesis; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000037:antagonists & inhibitors*; D009474:Neurons / Q000187:drug effects; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D014316:Tritium; D000097763:Polypeptide N-acetylgalactosaminyltransferase
D000911:Antibodies, Monoclonal; D016632:Apolipoprotein A-I; D005690:Galactose; D005732:Gangliosides; D017350:N-Acetylgalactosaminyltransferases; D010446:Peptide Fragments; D014316:Tritium; D000097763:Polypeptide N-acetylgalactosaminyltransferase; C023220:(N-acetylneuraminyl)-galactosylglucosylceramide N-acetylgalactosaminyltransferase