Identification of epidermal growth factor receptor in human buccal mucosa

EGF receptor was identified and its binding characteristics were determined. Buccal mucosa was obtained from 12 healthy volunteers (6 males and 6 females) and assayed individually for [¹²⁵I]-EGF binding. The specific binding of [¹²⁵I]-EGF to the receptor ranged from 2.85 to 6.12 fmol/mg protein. There was no significant difference in binding between male and female (4.31 ± 0.61 versus 3.94 ± 0.53 fmol/mg protein; mean ± SEM). Individual tissue homogenates were pooled for Scatchard analysis and cross-linking experiments. Scatchard analysis produced curvilinear plots with a K_d of 0.71 nM and B_max of 0.024 pmol/mg protein for the high-affinity binding sites, and K_d of 435 nM and B_max of 9.92 pmol/mg protein for the low-affinity binding sites. To determine the molecular weight of the EGF receptor, the [¹²⁵I]-EGF and receptor complex were cross-linked by DSS and subjected to SDS-PAGE. The autoradiogram of the gel revealed one major protein band of 160 K and a minor band of 170 K, characteristics shared with the EGF receptors in other tissues. The study is thought to be the first to demonstrate the presence of the EGF receptor in human buccal tissue and to show its biochemical features.