(2,6-diamino-5-thiocyanatopyridin-3-yl) thiocyanate, also designated as PR-619, is a broad-range reversible and cell-permeable inhibitor of deubiquitylating enzyme (DUB)[1][2][3], potently suppresses the activity of almost all cysteine protease DUBs[4], but shows selectivity toward DUBs over other proteases, such as calpain 1, or cathepsins[3]. PR-619 induces (tumor) cell death with EC50 values in the low micromolar range [1].
Deubiquitylating enzyme (DUB), also called ubiquitin isopeptidase or deubiquitinating proteins, performs deubiquitination of target proteins. Ubiquitination, followed by proteasomal degradation, is a process of ubiquitin proteasome system (UPS). Failure of the ubiquitin proteasome system (UPS) and/or the autophagy pathway may result in aggregation of proteins, a pathological hallmark of many neurodegenerative diseases [2].
In OLN-t40 cells, 7-10 μM as the concentration range for PR-619 to exert its cytotoxicity was suggested, half maximal cytotoxicity was observed after a 24h-treatment with 9-10 μM PR-619. Similar to MG-132, PR-619 caused an increase in the abundance of ubiquitinated proteins within 24 h at the concentration range of 7-12.5μM. Tested with OLN-t40 cells, PR-619, unlike MG-132, did not inhibit the enzymatic activity of the proteasome in cellular lysates but only when taken up by living cells[2]. An in vitro system showed that PR-619 was able to stabilize the microtubule network and led to small tau aggregates surrounding the microtubule organizing center [5].
There is still not any available result regarding in vivo treatment in an animal body.
References:
[1]. Mikael Altun, Holger B. Kramer, Lianne I. Willems, et al. Activity-Based Chemical Proteomics Accelerates Inhibitor Development for Deubiquitylating Enzymes. Chemistry & Biology, 2011, 18(11): 1401-1412.
[2]. Veronika Seiberlicha, Olaf Goldbauma, Victoria Zhukareva, et al. The small molecule inhibitor PR-619 of deubiquitinating enzymes affects the microtubule network and causes protein aggregate formation in neural cells: Implications for neurodegenerative diseases. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 2012, 1823(11): 2057–2068.
[3]. Iraia García-Santisteban, Godefridus J Peters, Elisa Giovannetti, et al. USP1 deubiquitinase: cellular functions, regulatory mechanisms and emerging potential as target in cancer therapy. Molecular Cancer, 2013, 12:91.
[4]. Maria Stella Ritorto, Richard Ewan, Ana B. Perez-Oliva, et al. Screening of DUB activity and specificity by MALDI-TOF mass spectrometry. Nature Communications, 2014, 5:4763.
[5]. Laura J Blair, Bo Zhang and Chad A Dickey, et al. Potential synergy between tau aggregation inhibitors and tau chaperone modulators. Alzheimer's Research & Therapy, 2013, 5:41.