TENASCIN CYTOTACTIN EGF-LIKE REPEATS - NOVEL MATRIKINE LIGANDS FOR THE EPIDERMAL GROWTH FACTOR RECEPTOR

摘要: Select epidermal growth factor (EGF)-like (EGFL) repeats of human tenascin cytotactin can stimulate EGF receptor (EGFR) signaling, but activation requires micromolar concentrations soluble EGFL in contrast to subnanomolar EGF. Using silico homology modeling techniques, we generated a structure for one such repeat, the 14th repeat (Ten14). Ten14 assumes tight EGF-like fold with truncated loops, consistent circular dichroism studies. We bound structures EGFR using two different approaches, resulting distinctly conformations. Normal mode analysis both indicated that binding pocket exhibits significantly higher mobility Ten14-EGFR complex compared EGF-EGFR complex; attributed this loss key high-affinity interactions within complex. proved efficacy our models by vitro experiments. Surface plasmon resonance measurements yielded equilibrium constant KD 74µM Ten14, approximately three orders magnitude weaker than In accordance predicted models, monomeric form does not bind sufficient stability induce degradation receptor, or undergo EGFR-mediated internalization. This transient interaction on cell surface is marked other ligands which cause transit through, and signaling from intracellular locales addition signaling. investigated whether Ten14-mediated restriction resulted altered cellular responses Activation PLCa m-calpain, molecules associated migration, were noted even at sub-saturating doses Ten14. However, ERK/MAPK, p90RSK Elk1, factors affecting proliferation, remained low high concentrations. Similar profiles observed EGF-treated cells 4°C, maneuver limits demonstrated direct concurrent effect overall biophysical - sustained migration was lower levels activated PLCa, proliferation basal. present novel class potentially signal as part matrix, triggering select cascades leading directed response an otherwise pleiotropic receptor.