Subcellular structures involved in internalization and degradation of epidermal growth factor

✍ Scribed by Fine, Richard E. ;Goldenberg, Richard ;Sorrentino, Joseph ;Herschman, Harvey R.

• Book ID: 102924863
• Publisher: Wiley (John Wiley & Sons)
• Year: 1981
• Tongue: English
• Weight: 1012 KB
• Volume: 15
• Category: Article
• ISSN: 0275-3723
• DOI: 10.1002/jsscb.1981.380150304

✦ Synopsis

Abstract

Epidermal Growth Factor (EGF), a small polypeptide which acts as a mitogen for many cell types, has previously been shown to bind to a specific plasma membrane receptor on 3T3 cells. If ^125^I‐EGF is bound to 3T3 cells for one hour at 4°C, it remains predominantly associated with the plasma membrane‐containing fractions obtained by subjecting cell supernatants to equilibrium sedimentation on sucrose gradients. When binding is followed by a 10‐minute incubation at 37°C, over 50% of the ^125^I‐EGF is associated with two internal membrane‐containing peaks having higher densities than the plasma membrane. After one hour at 37°C, over 80% of the ^125^I‐EGF is degraded and removed from the cells.

The most rapidly labeled internal peak corresponds in density to brain‐coated vesicles (CVs). Antiserum prepared against coated vehicles from brain precipitates the ^125^I‐EGF in this peak. In addition, CVs containing ^125^I‐EGF can be co‐purified from 3T3 cells exposed to ^125^I‐EGF, using brain as a carrier. Several lines of evidence suggest that the other ^125^I‐EGF‐labeled intracellular peak is ^125^I‐EGF in lysosomes.

These results provide kinetic and biochemical evidence for a unidirectional pathway for EGF catabolism by 3T3 cells. EGF first binds to the plasma membrane bound receptors, is then moved to the cytoplasm in CVs, and finally appears in lysosomes, where it is degraded and released from the cells. Ten‐millimolar NH~4~Cl blocks lysosomal hydrolysis of EGF almost completely. Subsequently, EGF internalization is inhibited. This finding suggests that the pathway for EGF internalization and degradation is tightly coupled.