Structural dynamics at the active site of the cancer-associated flavoenzyme NQO1 probed by chemical modification with PMSF

A small molecule cryptotanshinone induces non-enzymatic NQO1-dependent necrosis in cancer cells through the JNK1/2/Iron/PARP/calcium pathway

Human NAD(P)H: quinone oxidoreductase 1 (NQO1) is a flavoenzyme expressed at high levels in multiple solid tumors, making it an attractive target for anticancer drugs. Bioactivatable drugs targeting NQO1, such as β-lapachone (β-lap), are currently in clinical trials for the treatment of cancer. β-Lap selectively kills NQO1-positive (NQO1+) cancer cells by inducing reactive oxygen species (ROS) via catalytic activation of NQO1. In this study, we demonstrated that cryptotanshinone (CTS), a naturally occurring compound, induces NQO1-dependent necrosis without affecting NQO1 activity. CTS selectively kills NQO1+ cancer cells by inducing NQO1-dependent necrosis. Interestingly, CTS directly binds to NQO1 but does not activate its catalytic activity. In addition, CTS enables activation of JNK1/2 and PARP, accumulation of iron and Ca2+, and depletion of ATP and NAD+. Furthermore, CTS selectively suppressed tumor growth in the NQO1+ xenograft models, which was reversed by NQO1 inhibitor and NQO1 shRNA. In conclusion, CTS induces NQO1-dependent necrosis via the JNK1/2/iron/PARP/NAD+/Ca2+ signaling pathway. This study demonstrates the non-enzymatic function of NQO1 in inducing cell death and provides new avenues for the design and development of NQO1-targeted anticancer drugs.

Structural dynamics and functional cooperativity of human NQO1 by ambient temperature serial crystallography and simulations

The human NQO1 (hNQO1) is a flavin adenine nucleotide (FAD)-dependent oxidoreductase that catalyzes the two-electron reduction of quinones to hydroquinones, being essential for the antioxidant defense system, stabilization of tumor suppressors, and activation of quinone-based chemotherapeutics. Moreover, it is overexpressed in several tumors, which makes it an attractive cancer drug target. To decipher new structural insights into the flavin reductive half-reaction of the catalytic mechanism of hNQO1, we have carried serial crystallography experiments at new ID29 beamline of the ESRF to determine, to the best of our knowledge, the first structure of the hNQO1 in complex with NADH. We have also performed molecular dynamics simulations of free hNQO1 and in complex with NADH. This is the first structural evidence that the hNQO1 functional cooperativity is driven by structural communication between the active sites through long-range propagation of cooperative effects across the hNQO1 structure. Both structural results and MD simulations have supported that the binding of NADH significantly decreases protein dynamics and stabilizes hNQO1 especially at the dimer core and interface. Altogether, these results pave the way for future time-resolved studies, both at x-ray free-electron lasers and synchrotrons, of the dynamics of hNQO1 upon binding to NADH as well as during the FAD cofactor reductive half-reaction. This knowledge will allow us to reveal unprecedented structural information of the relevance of the dynamics during the catalytic function of hNQO1.