A cysteine near the C-terminus of UCH-L1 is dispensable for catalytic activity but is required to promote AKT phosphorylation, eIF4F assembly, and malignant B-cell survival

• Published in: Cell death discovery 2019-12, Vol.5 (1), p.152-9, Article 152
• Main Authors: Hussain, Sajjad, Bedekovics, Tibor, Ali, Asma, Zaid, Omar, May, Danielle G., Roux, Kyle J., Galardy, Paul J.
• Format: Article
• Language: English
• Subjects: 631/67/1990/291/1621/1915; 631/67/1990/804; 631/67/395; 631/80/82; 631/80/86/2369; AKT protein; Apoptosis; Biochemistry; Biomedical and Life Sciences; C-Terminus; Cell Biology; Cell Cycle Analysis; Cell survival; Life Sciences; Lymphocytes B; Phosphorylation; Stem Cells
• ISSN: 2058-7716; 2058-7716
• DOI: 10.1038/s41420-019-0231-1

The enzyme UCH-L1 is a neuro-endocrine and germinal center B-cell marker that contributes to the development and aggressive behavior of mature B-cell malignancies. While mutations in this enzyme have been associated with Parkinson’s disease, relatively little is known about the molecular features associated with the biochemical activities of UCH-L1. Here we use a survival-based complementation assay and site-directed mutagenesis and identify a novel role for the C-terminus of UCH-L1 in supporting cell survival. The C220 residue is required for UCH-L1 to promote the assembly of mTOR complex 2 and phosphorylation of the pro-survival kinase AKT. While this residue was previously described as a potential farnesylation site, destruction of the putative CAAX motif by adding a C-terminal epitope tag did not interfere with cell survival, indicating an alternate mechanism. We used proximity-based proteomics comparing the proteomes of wild-type and C220S UCH-L1 and identified a selective loss of association with RNA-binding proteins including components of the translation initiation machinery. As a consequence, the C220S mutant did not promote the assembly of the eIF4F complex. These data identify a novel role for the C-terminus of UCH-L1 in supporting pro-survival and metabolic activities in malignant B-cells. This finding may lead to the development of therapeutics with selective activity towards malignancy that potentially avoid neuronal toxicities.