Discovery of inhibitors that elucidate the role of UCH-L1 activity in the H1299 lung cancer cell line

Neuronal ubiquitin C-terminal hydrolase (UCH-L1) has been linked to Parkinson's disease (PD), the progression of certain nonneuronal tumors, and neuropathic pain. Certain lung tumor-derived cell lines express UCH-L1 but it is not expressed in normal lung tissue, suggesting that this enzyme plays a role in tumor progression, either as a trigger or as a response. Small-molecule inhibitors of UCH-L1 would be helpful in distinguishing between these scenarios. By utilizing high-throughput screening (HTS) to find inhibitors and traditional medicinal chemistry to optimize their affinity and specificity, we have identified a class of isatin O-acyl oximes that selectively inhibit UCH-L1 as compared to its systemic isoform, UCH-L3. Three representatives of this class (30, 50, 51) have IC(50) values of 0.80-0.94 micro M for UCH-L1 and 17-25 micro M for UCH-L3. The K(i) of 30 toward UCH-L1 is 0.40 micro M and inhibition is reversible, competitive, and active site directed. Two isatin oxime inhibitors increased proliferation of the H1299 lung tumor cell line but had no effect on a lung tumor line that does not express UCH-L1. Inhibition of UCH-L1 expression in the H1299 cell line using RNAi had a similar proproliferative effect, suggesting that the UCH-L1 enzymatic activity is antiproliferative and that UCH-L1 expression may be a response to tumor growth. The molecular mechanism of this response remains to be determined

Chaperone-mediated hierarchical control in targeting misfolded proteins to aggresomes

Not only do molecular chaperones assist protein folding, they also facilitate the degradation of misfolded polypeptides. In coordinating with cochaperones CHIP and BAG3, Hsp70 can also target misfolded proteins to aggresomes, thereby protecting cells from proteotoxic stress