Elevated levels of glycoprotein gp200 in progeria fibroblasts

The glycosylation of proteins in fibroblasts from people with the premature ageing disease Hutchinson-Gilford Progeria Syndrome (progeria) was investigated. Protein was prepared from fibroblast cell lines established from skin biopsy taken from progeria patients and control donors. Glycoproteins were labelled by the covalent attachment of the steroid hapten digoxygenin to the sugar group. After separation of total protein by SDS-PAGE and electroblotting onto Immobilon-PTM, glycoproteins were detected by enzyme immunoassay. We have observed a glycoprotein of M(r) 200 kDa which is consistently present in protein preparations from progeria fibroblasts and which is absent, or markedly reduced, in preparations from control fibroblasts. This suggests that it may be useful as a marker for progeria. Similar analysis of progeria lymphoblast and control lymphoblast cultures did not show this altered pattern of glycosylated proteins, indicating that it may be cell-type specific. Glycoproteins were also detected by labelling fibroblasts in vitro with D-[6-3H]glucosamine hydrochloride followed by SDS-PAGE of isolated protein and subsequent fluorography. Profiles of glycoproteins from progeria and control fibroblasts were consistent with those obtained from labelling of carbohydrate groups with digoxygenin. Protease digestion of cell protein verified that the band at M(r) 200 kDa contains a protein core. Characteristic features of progeria primarily involve the connective tissue and include wrinkled and loose skin, loss of soft tissue, thin limbs and stiff joints. Death of progeria patients is usually a result of cardiovascular abnormalities. The most consistent manifestations thus involve the connective tissue. The glycoprotein of M(r) 200 kDa which we have observed in progeria fibroblasts in vitro could reflect a perturbation in glycosylation which may underly the connective tissue defects seen in progeria.