Targeting the PD-1/PD-L1 immunologic checkpoint with monoclonal antibodies has provided unprecedented results in cancer treatment in the recent years. Development of chemical inhibitors for this pathway lags the antibody development because of insufficient structural information. The first nonpeptidic chemical inhibitors that target the PD-1/PD-L1 interaction have only been recently disclosed by Bristol-Myers Squibb. Here, we show that these small-molecule compounds bind directly to PD-L1 and that they potently block PD-1 binding. Structural studies reveal a dimeric protein complex with a single small molecule which stabilizes the dimer thus occluding the PD-1 interaction surface of PD-L1s. The small-molecule interaction “hot spots” on PD-L1 surfaces suggest approaches for the PD-1/PD-L1 antagonist drug discovery.

This study reports a new mechanism of cAMP mediated relaxation of Ca2+sensitized force, in smooth muscle (SM) through Epac, a GTP exchange factor for the small GTPase Rap1 which results in suppression of RhoA activity. We find that Epac selective cAMP analogue, 8‐pCPT‐2′‐O‐Me‐cAMP (007), significantly reduced agonist‐induced contractile force, in both intact and permeabilized vascular, gut and airway SM. Responses to 007 were independent of PKA and PKG. Activation of Epac resulted in increased Rap1·GTP accompanied by a significant decrease in RhoA activity and reductions in phosphorylation of RLC20 and MLCP. Transcriptional regulation of SM α‐actin and SM22, known to be regulated by RhoA, was also significantly decreased by activation of Epac. Forskolin, the phosphodiesterase inhibitor IBMX and isoproterenol significantly increased Rap1·GTP in rat aortic SM cells. Over‐expression of wild‐type Epac but not dominant negative Epac1R279E increased Rap1 activation after 007 stimulation. LPA‐induced activation of RhoA activity was reduced by treatment with 007 in WT but not Rap1B null fibroblasts. All together, our findings show a novel signaling mechanism whereby activation of Epac via cAMP results in PKA independent, Rap1 dependent Ca2+ desensitization of force in SM.

DAPK1 and ZIPK (also called DAPK3) are closely related serine/threonine protein kinases that regulate programmed cell death and phosphorylation of non-muscle and smooth muscle myosin. We have developed a fluorescence linked enzyme chemoproteomic strategy (FLECS) for the rapid identification of inhibitors for any element of the purinome and identified a selective pyrazolo[3,4-d]pyrimidinone (HS38) that inhibits DAPK1 and ZIPK in an ATP-competitive manner at nanomolar concentrations. In cellular studies, HS38 decreased RLC20 phosphorylation. In ex vivo studies, HS38 decreased contractile force generated in mouse aorta and rabbit ileum, and calyculin A stimulated arterial muscle by decreasing RLC20 and MYPT1 phosphorylation. The inhibitor also promoted relaxation in Ca2+-sensitized vessels. A close structural analogue (HS43) with 5-fold lower affinity for ZIPK produced no effect on cells or tissues. These findings are consistent with a mechanism of action wherein HS38 specifically targets ZIPK in smooth muscle. The discovery of HS38 provides a lead scaffold for the development of therapeutic agents for smooth muscle related disorders and a chemical means to probe the function of DAPK1 and ZIPK across species.

Palladin, an actin associated protein, plays a significant role in regulating cell adhesion and cell motility. Palladin is important for development, as knockdown in mice is embryonic lethal, yet its role in the development of the vasculature is unknown. We have shown that palladin is essential for the expression of smooth muscle cells (SMC) marker genes and force development in response to agonist stimulation in palladin deficient SMCs. The goal of the study was to determine the molecular mechanisms underlying palladin's ability to regulate the expression of SMC marker genes. Results showed that palladin expression was rapidly induced in an A404 cell line upon retinoic acid (RA) induced differentiation. Suppression of palladin expression with siRNAs inhibited the expression of RA induced SMC differentiation genes, SM α-actin (SMA) and SM22, whereas over-expression of palladin induced SMC gene expression. Chromatin immunoprecipitation assays provided evidence that palladin bound to SMC genes, whereas co-immunoprecipitation assays also showed binding of palladin to myocardin related transcription factors (MRTFs). Endogenous palladin was imaged in the nucleus, increased with leptomycin treatment and the carboxyl-termini of palladin co-localized with MRTFs in the nucleus. Results support a model wherein palladin contributes to SMC differentiation through regulation of CArG-SRF-MRTF dependent transcription of SMC marker genes and as previously published, also through actin dynamics. Finally, in E11.5 palladin null mouse embryos, the expression of SMA and SM22 mRNA and protein is decreased in the vessel wall. Taken together, our findings suggest that palladin plays a key role in the differentiation of SMCs in the developing vasculature.

Objective Small GTPase Rap1b controls several basic cellular phenomena and its deletion in mice leads to several cardiovascular defects, including impaired adhesion of blood cells and defective angiogenesis. We found that Rap1b knockout (Rap1b−/−) mice develop cardiac hypertrophy and hypertension. Therefore, we examined the function of Rap1b in regulation of blood pressure. Approach and Results Rap1b−/− mice developed cardiac hypertrophy and elevated blood pressure, but maintained a normal heart rate. Correcting elevated blood pressure with losartan, an angiotensin II type I receptor alleviated cardiac hypertrophy in Rap1b−/− mice, suggesting a possibility that cardiac hypertrophy develops secondary to hypertension. The indices of renal function and plasma renin activity were normal in Rap1b−/− mice. Ex vivo, we examined whether the effect of Rap1b-deletion on smooth muscle (SM)-mediated vessel contraction and endothelium-dependent vessel dilation, two major mechanisms controlling basal vascular tone, were the basis for the hypertension. We found increased contractility upon stimulation with a thromboxane analogue or Angiotensin II or phenylephrine along with increased inhibitory phosphorylation of myosin phosphatase under basal conditions consistent with elevated basal tone and the observed hypertension. cAMP-dependent-relaxation in response to Rap1 activator, Epac, was decreased in vessels from Rap1b−/− mice. Defective endothelial release of dilatory nitric oxide (NO) in response to elevated blood flow leads to hypertension. We found that NO-dependent vasodilation was significantly inhibited in Rap1b-deficient vessels. Conclusion This is the first report to indicate that Rap1b in both SM and endothelium plays a key role in maintaining blood pressure by controlling normal vascular tone.

SummaryUSP2a is a deubiquitinase responsible for stabilization of cyclin D1, a crucial regulator of cell-cycle progression and a proto-oncoprotein overexpressed in numerous cancer types. Here we report that lithocholic acid (LCA) derivatives are inhibitors of USP proteins, including USP2a. The most potent LCA derivative, LCA hydroxyamide (LCAHA), inhibits USP2a, leading to a significant Akt/GSK3β-independent destabilization of cyclin D1, but does not change the expression of p27. This leads to the defects in cell-cycle progression. As a result, LCAHA inhibits the growth of cyclin D1-expressing, but not cyclin D1-negative cells, independently of the p53 status. We show that LCA derivatives may be considered as future therapeutics for the treatment of cyclin D1-addicted p53-expressing and p53-defective cancer types.

BackgroundMyeloperoxidase (MPO) impairing endothelial functions. We investigated whether increasing concentration of myeloperoxidase (MPO) and inflammatory markers induce progression and incident acute coronary syndrome (ACS) in stable coronary artery disease (SCAD) patients. Therefore, the concentration of MPO, lipids, lipoproteins (apo(apolipoprotein) AI, apoB, lipoprotein associated phospholipase A2 (LpPLA2) level), inflammatory markers (high sensitivity C-reactive protein (hsCRP), tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6) concentration) were examined.MethodsThis study concerned 67 SCAD patients divided into groups: all patients, patients with MPO < 200 ng/ml, MPO 200–300 ng/ml, MPO > 300 ng/ml concentration and 15 controls. ApoAI, apoB and hsCRP levels were examined using the immunonephelometric method, and MPO, LpPLA2, IL-6, TNF-α concentration was performed by using Quantikine ELISA kit R&D Systems.ResultsIn the all patients, and in group with MPO 200–300 ng/ml TC, LDL-C, nonHDL-C, LpPLA2 concentration and TC/HDL-C, LDL-C/HDL-C ratios were insignificant, and significantly higher concentration of TG, apoB, MPO, inflammatory markers and TG/HDL-C, MPO/apoAI, MPO/HDL-C ratios but HDL-C, apoAI level and HDL-C/apoAI ratio were significantly reduced. In the group of patients with MPO < 200 ng/ml, level of TC, LDL-C, nonHDL-C, apoAI, apoAII, LpPLA2 and MPO and LDL-C/HDL-C ratio were in-significant, HDL-C was decreased but apoB, TG, inflammatory markers, apoB/apoAI, TG/HDL-C, MPO/apoAI, MPO/HDL-C ratio were significantly increased. In the group of patients with MPO > 300 ng/ml concentration of TC, LDL-C, nonHDL-C, apoAII, LpPLA2 and LDL-C/HDL-C ratios were not significant, but HDL-C and apoAI concentrations were significantly decreased. The concentrations of TG, apoB, MPO and inflammatory markers and TG/HDL-C, MPO/apoAI, MPO/HDL-C ratios were significantly increased compared to the controls. The apoAI concentration was significantly decreased and the concentration of MPO and hsCRP as well as MPO/apoAI and MPO/HDL-C ratios were significantly higher as compared to the group of patients with MPO < 200 ng/ml.Spearman’s correlation test showed a positive correlation between MPO concentration and MPO/apoAI and MPO/HDL-C ratios in all patients and MPO < 200 ng/ml, MPO 200–300 ng/ml. The patients with MPO > 300 ng/ml showed a positive correlation between the concentration of MPO and the level of hsCRP and IL-6, and a negative correlation between MPO/apoAI ratio and the concentration of HDL-C, apoAI and apoAII.ConclusionThe results suggest that moderate dyslipidemia and dyslipoproteinemia deepening of inflammation, and inflammation slowly induce increase MPO concentration which decrease apoAI and HDL-C level and disturb HDLs function. The increasing MPO level and MPO/HDL-C, MPO/apoAI ratios can differentiate the SCAD patients at the risk of acute coronary syndrome (ACAD) and stroke.

USP2a is a deubiquitinating protease that rescues its target proteins from destruction by the proteasome by reversing the process of protein ubiquitination. USP2a shows oncogenic properties in vivo and has been found to be a specific activator of cyclin D1. Many types of cancers are addicted to cyclin D1 expression. Targeting USP2a is a promising strategy for cancer therapy but little progress has been made in the field of inhibition of USP2a. Using NMR-based fragment screening and biophysical binding assays, we have discovered small molecules that bind to USP2a. Iterations of fragment combination and structure-driven design identified two 5-(2-thienyl)-3-isoxazoles as the inhibitors of the USP2a-ubiquitin protein-protein interaction. The affinity of these molecules for the catalytic domain of USP2a parallels their ability to interfere with USP2a binding to ubiquitin in vitro. Altogether, our results establish the 5-(2-thienyl)-3-isoxazole pharmacophore as an attractive starting point for lead optimization.