HOMOGENEOUS ESCHERICHIA-COLI CHAPERONIN-60 INDUCES IL-1-BETA AND IL-6GENE-EXPRESSION IN HUMAN MONOCYTES BY A MECHANISM INDEPENDENT OF PROTEIN CONFORMATION

Escherichia coli chaperonin (cpn) 60 (groEL) is a protein-folding olig omer lacking tryptophan residues that copurifies with tryptophan-conta ining proteins and peptides, Cpn 60 is a major immunogen in infectious diseases, and evidence suggests that groEL and mycobacterial cpn 60s can induce cytokine synthesis, stimulate cytokine-dependent bone resor ption, and up-regulate expression of vascular endothelial cell adhesio n molecules. Whether such activities are due to the cpn 60 or to the c opurifying/contaminating proteins/peptides has not been determined. He re we report a method for removing the protein contaminants of groEL a nd demonstrate that this, essentially homogeneous, groEL remains a pot ent inducer of human monocyte IL-1 beta and IL-6 production. Contamina ting peptides had no cytokine-inducing activity and did not synergize with purified groEL. The LPS inhibitor polymyxin B and the CD14-neutra lizing Ab MY4 had no inhibitory action on groEL demonstrating that act ivity is not due to LPS contamination, Heating groEL had no effect on its capacity to stimulate human monocytes to secrete IL-6, Proteolysis of groEL with trypsin, sufficient to produce low molecular mass pepti des, also had no inhibitory effect, Thus, we conclude that groEL is a potent inducer of monocyte proinflammatory cytokine production, which acts through the binding of nonconformational peptide domains that are conserved after proteolysis. These data suggest that if groEL aas rel eased from bacteria it could induce prolonged tissue pathology by virt ue of its cytokine-inducing activity and its resistance to proteolytic inhibition of bioactivity.