Monoclonal antibodies to desmosomes in structural analysis of adhesion molecules and tumour diagnosis

Parrish, Elaine Patricia (1987) Monoclonal antibodies to desmosomes in structural analysis of adhesion molecules and tumour diagnosis. University of Southampton, Doctoral Thesis.

Abstract

Desmosomes are adhesive intercellular junctions, characteristic of most vertebrate epithelia. Previous immunological and biochemical studies have identified two desmosomal glycoproteins, dg 2 and dg 3, of 130,000 and 115,000 Mr, as the desmosomal adhesion molecules. The primary aim of this project was to use monoclonal antibodies against these molecules to study their structure. A monoclonal antibody which reacted with the intracellular domains of dg 2 and 3 was obtained, suggesting that both molecules span the plasma membrane. Immunoblotting of tryptic fragments derived from whole cells, suggested that the cytoplasmic domain of dg 2 may be larger than that of dg 3. Labelling with ³²P-phosphate, immunoprecipitation with polyclonal antisera and phosphamino acid analysis, indicated that dg 2 was phosphorylated on serine, but that dg 3 was not. Thus, by two criteria dg 2 and 3 show heterogeneity in their cytoplasmic domains. A linear model for the structure of dg 2 and 3, showing their transmembrane disposition, was constructed on the basis of these data. Phosphorylation of dg 2 did not occur in MDCK cells when the extracellular [Ca²⁺] was below that which permits desmosome formation (i.e. < 50 μM). Phosphorylation of dg 2 may therefore have a role in desmosome formation. An affinity column made with the monoclonal antibody against dg 2 and 3, was used to purify a 30,000 (Mr) tryptic fragment of dg 2 and 3 from bovine nasal epithelial desmosomes. Some mouse polyclonal antisera to dg 2 and 3 showed restricted tissue specificity, reacting only with the meninges and suprabasal skin cells. The staining pattern on epidermis may indicate that dg 2 and 3 undergo changes during terminal differentiation and stratification. A monoclonal antibody against the 250,000 and 215,000 Mr proteins of desmosomes was shown to be a reliable marker for meningiomas and metastatic carcinomas in the diagnosis of intracranial tumours.(DX90542)

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