IDENTIFICATION OF DIFFERENTIALLY GLYCOSYLATED FORMS OF THE SOLUBLE P75 TUMOR-NECROSIS-FACTOR (TNF) RECEPTOR IN HUMAN URINE

Human urine is known to contain a 30 kDa soluble form of the p75-TNF r eceptor (sTNF-R2), In this work we have purified sTNF-R2 from the urin e of normal subjects and further characterized its structure and activ ity. sTNF-R2 was resolved by reducing SDS-PAGE in a major band of 30 k Da, similar in size to the previously described urinary sTNFR2, and in a minor band of 45 kDa, ''Western'' blotting analysis with anti-TNF-R 1 and anti-TNF-R2 antibodies showed that both bands were immunological ly related to the membrane TNF-R2. Glycosylation studies indicated tha t the 30 kDa is N-glycosylated while the 45 kDa form is N- and O-glyco sylated, and suggested that both forms contain terminally linked siali c acid that is differentially recognized by lectins. These results ind icate that human urine contains, besides the 30 kDa form, a new form o f 45 kDa characterized by different glycosylation type and degree.