Differential heat stress stability of epidermal growth factor receptor and erbB-2 receptor tyrosine kinase activities

✍ Scribed by Samuel M. Liu; Graham Carpenter

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 637 KB
• Volume: 157
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041570205

✦ Synopsis

Abstract

The epidermal growth factor (EGF) and __erb__B‐2 receptors are structurally related membrane‐bound tyrosine kinases. While these proteins exhibit close sequence homology, 50% overall and 80% in the tyrosine kinase domains, they respond very differently to heat stress. In NIH‐3T3 or NR6 cells transfected with wild‐type EGF‐R and incubated at 37°C or heat shocked at 46°C, EGF binds to its receptor and stimulates receptor autophosphorylation to equivalent extents. At 46°C, however, the basal tyrosine kinase activity of the wild‐type __erb__B‐2 receptor is rapidly lost. When cells containing chimeric receptors composed of the EGF‐R extracellular domain and intracellular domain of __erb__B‐2 were heat stressed, ^125^I‐EGF bound to the receptors, but did not stimulate receptor autophosphorylation. The decline in EGF‐stimulated chimeric __erb__B‐2 receptor autophosphorylation is dependent on the length of heat shock, with nearly 100% of the kinase activity lost after 60 min at 46°C. The loss of chimeric receptor __erb__B‐2 kinase activity is not due to degradation of receptor protein, nor is it attributable to a specific transmembrane domain from either the EGF or __erb__B‐2 receptors. Sensitivity of __erb__B‐2 to heat stress is also not a result of denaturation of this receptor's carboxy‐terminal domain. Insertion of the __erb__B‐2 tyrosine kinase domain into the EGF‐R confers heat stress sensitivity to the resultant chimeric receptor. Thus, although the EGF‐R and __erb__B‐2 kinase domains show a high degree of homology, the secondary/tertiary structures of these domains would seem to be stabilized in distinct manners. © 1993 Wiley‐Liss, Inc.