TY - JOUR
T1 - Intracellular trafficking of epidermal growth factor family ligands is directly influenced by the pH sensitivity of the receptor/ligand interaction
AU - French, A. R.
AU - Tadaki, D. K.
AU - Niyogi, S. K.
AU - Lauffenburger, D. A.
PY - 1995/3/3
Y1 - 1995/3/3
N2 - Using members of the epidermal growth factor (EGF) family as well as site- directed recombinant human EGF mutants, we investigated how ligand binding properties influence endosomal sorting. Mouse EGF (mEGF), human EGF (hEGF), and transforming growth factor α (TGFα) bind to the human EGF receptor (EGFR) with similar affinities at pH 7.4. However, the binding properties of these ligands have substantially different pH sensitivities resulting in varying degrees of dissociation from the receptors at lower pH levels characteristic of endosomes. We employed a steady-state sorting assay to determine the fraction of ligand sorted to recycling versus degradation as a function of the number of intracellular ligand molecules in mouse B82 fibroblasts. mEGF, hEGF, and TGFα display significantly different steady- state endosomal sorting patterns which correspond to the extent of their dissociation at endosomal pH. Moreover, several recombinant hEGF mutants with differing affinities exhibit altered endosomal sorting compared to hEGF, demonstrating a similar direct relationship between ligand binding properties and endosomal sorting outcomes. Intracellular trafficking of the EGF ligands was also monitored by measuring the observed degradation rate constants. These likewise show marked differences that correlate with the differing pH sensitivities of the ligands' binding properties.
AB - Using members of the epidermal growth factor (EGF) family as well as site- directed recombinant human EGF mutants, we investigated how ligand binding properties influence endosomal sorting. Mouse EGF (mEGF), human EGF (hEGF), and transforming growth factor α (TGFα) bind to the human EGF receptor (EGFR) with similar affinities at pH 7.4. However, the binding properties of these ligands have substantially different pH sensitivities resulting in varying degrees of dissociation from the receptors at lower pH levels characteristic of endosomes. We employed a steady-state sorting assay to determine the fraction of ligand sorted to recycling versus degradation as a function of the number of intracellular ligand molecules in mouse B82 fibroblasts. mEGF, hEGF, and TGFα display significantly different steady- state endosomal sorting patterns which correspond to the extent of their dissociation at endosomal pH. Moreover, several recombinant hEGF mutants with differing affinities exhibit altered endosomal sorting compared to hEGF, demonstrating a similar direct relationship between ligand binding properties and endosomal sorting outcomes. Intracellular trafficking of the EGF ligands was also monitored by measuring the observed degradation rate constants. These likewise show marked differences that correlate with the differing pH sensitivities of the ligands' binding properties.
UR - http://www.scopus.com/inward/record.url?scp=0028969961&partnerID=8YFLogxK
U2 - 10.1074/jbc.270.9.4334
DO - 10.1074/jbc.270.9.4334
M3 - Article
C2 - 7876195
AN - SCOPUS:0028969961
SN - 0021-9258
VL - 270
SP - 4334
EP - 4340
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 9
ER -