Lithium chloride inactivates the 20S proteasome from WEHI-3B D + leukemia cells

• Published in: Biochemical and biophysical research communications Vol. 303; no. 4; pp. 1058 - 1064
• Main Authors: Holtz, Kathleen M., Rice, Anna M., Sartorelli, Alan C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18.04.2003
• Subjects: Animals; Chymotrypsin - metabolism; Chymotrypsin-like activity; Cysteine Endopeptidases - drug effects; Cysteine Endopeptidases - isolation & purification; Cysteine Endopeptidases - metabolism; Cysteine Proteinase Inhibitors - pharmacology; Kinetics; Leukemia - enzymology; LiCl; Lithium Chloride - pharmacology; Multienzyme Complexes - drug effects; Multienzyme Complexes - isolation & purification; Multienzyme Complexes - metabolism; Peptidyl-glutamyl peptide hydrolyzing activity; Proteasome; Proteasome Endopeptidase Complex; Tumor Cells, Cultured; WEHI-3B D; Peptidyl-glutamyl peptide hydrolyzing activity; LiCl; WEHI-3B D; Proteasome; Chymotrypsin-like activity
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/S0006-291X(03)00473-X

LiCl interacts synergistically with all- trans-retinoic acid, promoting the terminal differentiation of WEHI-3B D + cells, a phenomenon partially due to the ability of the monovalent lithium cation to inhibit the proteasome-dependent degradation of retinoic acid receptor α protein. In this report, the 20S proteasome was purified from WEHI-3B D + cells and the effects of LiCl on chymotrypsin-like (Chtl) activity and peptidyl-glutamyl peptide hydrolyzing (PGPH) activity were determined. LiCl functions to inactivate both proteasomal activities in a time-dependent manner, without affecting non-proteasomal proteases. The half-lives for inactivation of Chtl and PGPH hydrolyzing activities were approximately 23 and 36 min, respectively, at 10 mM LiCl. Both SDS and peptide substrate increased the rate of inactivation. Partial enzymatic activity was recovered after dialysis in the absence of SDS, indicating that the off-rate for lithium was extremely slow. The findings suggest that the inactivation of Chtl and PGPH activities by LiCl occurs through a proteasomal conformational change.