Discovery and Characterization of a Novel Series of Chloropyrimidines as Covalent Inhibitors of the Kinase MSK1

We describe the identification and characterization of a series of covalent inhibitors of the C-terminal kinase domain (CTKD) of MSK1. The initial hit was identified via a high-throughput screening and represents a rare example of a covalent inhibitor which acts via an S_NAr reaction of a 2,5-dichloropyrimidine with a cysteine residue (Cys440). The covalent mechanism of action was supported by in vitro biochemical experiments and was confirmed by mass spectrometry. Ultimately, the displacement of the 2-chloro moiety was confirmed by crystallization of an inhibitor with the CTKD. We also disclose the crystal structures of three compounds from this series bound to the CTKD of MSK1, in addition to the crystal structures of two unrelated RSK2 covalent inhibitors bound to the CTKD of MSK1.

Secretory characteristics and viability of human term placental tissue after overnight cold preservation

Collection of human term placentae for research purposes is generally limited during working hours. Preserving placental tissue overnight might help to postpone experiments and, by extent, to increase material availability. In this study, fragments from normal placentae were incubated at 37 degrees C either immediately after delivery or after preservation at 4 degrees C in a HEPES-buffered solution or in a Roswell Park Memorial Institute (RPMI) 1640 culture medium. Protein, human chorionic gonadotrophin (HCG), human placental lactogen (HPL) and lactate dehydrogenase (LDH) contents within preserved explants were similar to those within freshly delivered ones. In contrast, HCG and HPL amounts released during incubation of preserved tissue were lower than with freshly delivered tissue. Differences were significant only during the first 3 h of incubation. Hormone releases were similarly Ca(2+)-stimulated, and Co(2+)- and low temperature-inhibited in preserved and freshly delivered tissues. After preservation, LDH leakage was also reduced. Furthermore, before and after 37 degrees C incubation during 6 h, preserved tissue was morphologically indistinguishable from freshly delivered tissue and showed neither higher incidence of DNA fragmentation, nor elevated caspase-3 activity, both of which are markers of apoptosis. This study validates an original, useful and rapid method to preserve placental tissue. Consequently, this preservation model may facilitate the study of physiological processes regulating placental hormone secretion in normal and pathological conditions.