Recent data from the literature have shown that
cDNA clones for the carboxyterminal domain of the core
protein of large
proteoglycan monomers from human cartilage contain an
EGF-like domain, which appears to undergo alternative splicing. In the present study we have found that articular
proteoglycans from human and baboon separated on
agarose flat-bed
gels and blotted onto
nitrocellulose react with a rabbit antiserum to mouse
EGF. In addition both forms of the
proteoglycans (band I and band II) seen on these
gels are reactive. Reactivity is seen with
proteoglycans extracted from human articular cartilage of various ages (fetal, newborn, young and aged) and with
proteoglycans extracted from cartilage of
thanatophoric dysplasia and homozygous
achondroplasia. Reactivity is dependent on prior digestion of the
nitrocellulose blot with Chase ABC, suggesting masking of
epitope by
chondroitin sulfate. Reactivity of the
EGF antiserum with cartilage
proteoglycan core
protein was also demonstrated in an ELISA system with core
protein as coating
antigen. The reactivity appears to reside in a tryptic
peptide generated from Chase/
keratanase digested core
protein. The immunoreactive species migrates as a 68 KDa species on gradient
gels. Immunological detection and quantitative analysis of the
EGF-like domain could be useful for analysis of various
proteoglycan samples.