Cyclizidine-Type Alkaloids from Streptomyces sp HNA39
JOURNAL OF NATURAL PRODUCTS
Authors: Jiang, Yong-Jun; Li, Jia-Qi; Zhang, Hao-Jian; Ding, Wan-Jing; Ma, Zhong-Jun
Abstract
Eight new cyclizidine-type alkaloids (1-8) and one known alkaloid (9) were identified from the chemical investigations of a marine-derived actinomycete, Streptomyces sp. HNA39. Among these alkaloids, compounds 3, 7, and 8 contain a chlorine atom, and the known alkaloid, (+)-ent-cydizidine (9), is now first reported as a natural product. Their structures were elucidated by extensive NMR-spectroscopic analysis and HRESIMS data. The absolute configurations of all of the compounds were established by ECD calculations. Cytotoxicity evaluations of all of the compounds showed that compound 2 exhibited significant activity against the PC3 and HCT116 human cancer-cell lines with IC50 values of 0.52 +/- 0.03 and 8.3 +/- 0.1 mu M, respectively. Interestingly, compounds 2, 5, 7, and 8 exhibited moderate inhibition against the ROCK2 protein kinase with IC50 values from 7.0 +/- 0.8 to 42 +/- 3 mu M.
Rho Kinase Inhibition as a Therapeutic for Progressive Supranuclear Palsy and Corticobasal Degeneration
JOURNAL OF NEUROSCIENCE
Authors: Gentry, Erik G.; Henderson, Benjamin W.; Arrant, Andrew E.; Gearing, Marla; Feng, Yangbo; Riddle, Nicole C.; Herskowitz, Jeremy H.
Abstract
Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative four-repeat tauopathies with no cure. Mitigating pathogenic tau levels is a rational strategy for tauopathy treatment, but therapeutic targets with clinically available drugs are lacking. Here, we report that protein levels of the Rho-associated protein kinases (ROCK1 and ROCK2), p70 S6 kinase (S6K), and mammalian target of rapamycin (mTOR) were increased in PSP and CBD brains. RNAi depletion of ROCK1 or ROCK2 reduced tau mRNA and protein level in human neuroblastoma cells. However, additional phenotypes were observed under ROCK2 knockdown, including decreased S6K and phosphorylated mTOR levels. Pharmacologic inhibition of Rho kinases in neurons diminished detergent-soluble and -insoluble tau through a combination of autophagy enhancement and tau mRNA reduction. Fasudil, a clinically approved ROCK inhibitor, suppressed rough eye phenotype and mitigated pathogenic tau levels by inducing autophagic pathways in a Drosophila model of tauopathy. Collectively, these findings highlight the Rho kinases as rational therapeutic targets to combat tau accumulation in PSP and CBD.