Organ-specific off-target effects of Pim/ZIP kinase inhibitors suggest lack of contractile Pim kinase activity in prostate, bladder, and vascular smooth muscle

Smooth muscle contraction by Pim kinases and ZIPK has been suggested, but evidence for lower urinary tract organs or using Pim-selective inhibitor concentrations is not yet available. Here, we assessed effects of the Pim inhibitors AZD1208 and TCS PIM-1 and the dual ZIPK/Pim inhibitor HS38 on contractions of human prostate and bladder tissues and of porcine interlobar arteries. Human tissues were obtained from radical prostatectomy and radical cystectomy and renal interlobar arteries from pigs. Contractions were studied in an organ bath. Noradrenaline-, phenylephrine- and methoxamine-induced contractions were reduced (up to > 50%) with 500-nM AZD1208 in prostate tissues and to lesser degree and not consistently with all agonists in interlobar arteries. A total of 100-nM AZD1208 or 500-nM TCS PIM-1 did not affect agonist-induced contractions in prostate tissues. Decreases in agonist-induced contractions with 3-µM HS38 in prostate tissues and interlobar arteries were of small extent and did not occur with each agonist. Carbachol-induced contractions in detrusor tissues were unchanged with AZD1208 (500 nM) or HS38. Electric field stimulation-induced contractions were not affected with AZD1208 or HS38 in any tissue, but slightly reduced with 500-nM TCS PIM-1 in prostate tissues. Concentration-dependent effects of Pim inhibitors suggest lacking Pim-driven smooth muscle contraction in the prostate, bladder, and interlobar arteries but point to organ-specific functions of off-targets. Procontractile functions of ZIPK in the prostate and interlobar arteries may be limited and are lacking in the detrusor.

The effect of aspartame on accelerating caspase-dependent apoptosis of pancreatic islet via ZIPK/STAT3/caspase 3 signaling pathway

Aspartame (ASP) as an important sugar substitute is widely used in pharmaceutical and food processing. Here, we compared the effects of ASP and sucrose on mice pancreatic islet cells in vivo and observed that ASP with the condition of high concentration and long-term exposure (HASP) could cause insulin secretion (500 mg/kg for 1 month). Next, we conducted iTRAQ mass spectrometry to profile the global phosphoproteome and found that phosphorylation of zipper-interacting protein kinase (ZIPK) in murine pancreatic islet tissues were induced at Thr197, Thr242, Thr282, and Ser328 by high-sucrose (HS) treatment, but only induced at Thr197 and Ser328 by HASP treatment. Simultaneously, phosphorylation of STAT3 could be induced at Tyr705 and Ser727 by HS but not by HASP. Furthermore, presence of activated STAT3 accompanied with autophagy was observed in HS treatment. In turn, the inactivation of STAT3 as well as enhanced expression of caspase 3 was observed in HASP treatment. We generated Thr242APro and Thr282Pro on ZIPK using CRISPR-Cas9 in β-TC3 cells and found the weakened interaction with STAT3 as well as the reduced phosphorylation of STAT3 even under HS stimulation. Finally, we observed that ankyrin repeat domain containing 11 (ANKRD11) could interact with ZIPK and play an inhibitory role in the phosphorylation of Thr242APro and Thr282Pro of ZIPK. However, HASP can induce the retention of ANKRD11 in the cytoplasm by phenylpyruvic acid (the metabolite of ASP). Taken together, this study determined that ASP with high concentration and long-term exposure could lead to caspase-dependent apoptosis of pancreatic islet cells through ANKRD11/ZIPK/STAT3 inhibition. Our results give evidence of adverse effects of aspartame on islet cells in some extreme conditions, which might help people to reconsider the biosafety of non-nutritive sweeteners.

Elevated ZIPK is required for TNF-α-induced cell adhesion molecule expression and leucocyte adhesion in endothelial cells

Leucocyte adhesion to the vascular endothelium is a critical event in the early inflammatory response to infection and injury. This process is primarily regulated by the expression of cell adhesion molecules (CAMs) in endothelial cells. It has been well documented that tumor necrosis factor alpha (TNF-α) is a key regulator of CAM expression within this process, but its regulatory mechanism remains controversial. To investigate the scenario within this process, we assessed the role of zipper-interacting protein kinase (ZIPK), a serine/threonine kinase with multiple substrates, in CAM expression. We used TNF-α as inflammatory stimulator and found that ZIPK was integrated into the signaling regulation of TNF-α-mediated CAM expression. In human umbilical vein endothelial cells (HUVECs), TNF-α exposure led to significantly increased expression of both intercellular CAM-1 (ICAM-1) and vascular CAM-1 (VCAM-1), along with an increase in the adhesion of THP-1 monocytes to HUVECs. Simultaneously, ZIPK gene was also up-regulated at the transcription level. These effects were clearly inhibited by the ZIPK-specific inhibitor Tc-DAPK6 or small interfering RNA (siRNA) capable of specifically inhibiting ZIPK expression. We thus suggest that both ZIPK activation and ZIPK gene expression are necessary for TNF-α-mediated CAM expression and leucocyte adhesion. Interestingly, ZIPK inhibition also significantly suppressed TNF-α-induced nuclear factor kappa B (NF-κB) activation, indicating that TNF-α-mediated ZIPK expression functions upstream of NF-κB and CAM expression. We thus propose a TNF-α/ZIPK/NF-κB signaling axis for CAM expression that is necessary for leucocyte adhesion to endothelial cells. Our data in this study revealed a potential molecular target for exploring anti-inflammation drugs.

p116Rip promotes myosin phosphatase activity in airway smooth muscle cells

Myosin phosphatase-Rho interacting protein (p116^Rip ) was originally found as a RhoA-binding protein. Subsequent studies by us and others revealed that p116^Rip facilitates myosin light chain phosphatase (MLCP) activity through direct and indirect manners. However, it is unclear how p116^Rip regulates myosin phosphatase activity in cells. To elucidate the role of p116^Rip in cellular contractile processes, we suppressed the expression of p116^Rip by RNA interference in human airway smooth muscle cells (HASMCs). We found that knockdown of p116^Rip in HASMCs led to increased di-phosphorylated MLC (pMLC), that is phosphorylation at both Ser19 and Thr18. This was because of a change in the interaction between MLCP and myosin, but not an alteration of RhoA/ROCK signaling. Attenuation of Zipper-interacting protein kinase (ZIPK) abolished the increase in di-pMLC, suggesting that ZIPK is involved in this process. Moreover, suppression of p116^Rip expression in HASMCs substantially increased the histamine-induced collagen gel contraction. We also found that expression of the p116^Rip was decreased in the airway smooth muscle tissue from asthmatic patients compared with that from non-asthmatic patients, suggesting a potential role of p116^Rip expression in asthma pathogenesis.

Validation of chemical genetics for the study of zipper-interacting protein kinase signaling

Zipper-interacting protein kinase (ZIPK) is a Ser/Thr kinase that mediates a variety of cellular functions. Analogue-sensitive kinase technology was applied to the study of ZIPK signaling in coronary artery smooth muscle cells. ZIPK was engineered in the ATP-binding pocket by substitution of a bulky gatekeeper amino acid (Leu93) with glycine. Cell-permeable derivatives of pyrazolo[3,4-d]pyrimidine provided effective inhibition of L93G-ZIPK (1NM-PP1, IC₅₀ , 1.0 μM; 3MB-PP1, IC₅₀ , 2.0 μM; and 1NA-PP1, IC₅₀ , 8.6 μM) but only 3MB-PP1 had inhibitory potential (IC₅₀  > 10 μM) toward wild-type ZIPK. Each of the compounds also attenuated Rho-associated coiled-coil containing protein kinase (ROCK) activity under experimental conditions found to be optimal for inhibition of L93G-ZIPK. In silico molecular simulations showed effective docking of 1NM-PP1 into ZIPK following mutational enlargement of the ATP-binding pocket. Molecular simulation of 1NM-PP1 docking in the ATP-binding pocket of ROCK was also completed. The 1NM-PP1 inhibitor was selected as the optimal compound for selective chemical genetics in smooth muscle cells since it displayed the highest potency for L93G-ZIPK relative to WT-ZIPK and the weakest off-target effects against other relevant kinases. Finally, the 1NM-PP1 and L93G-ZIPK pairing was effectively applied in vascular smooth muscle cells to manipulate the phosphorylation level of LC20, a previously defined target of ZIPK.

Targeting Pim Kinases and DAPK3 to Control Hypertension

Sustained vascular smooth muscle hypercontractility promotes hypertension and cardiovascular disease. The etiology of hypercontractility is not completely understood. New therapeutic targets remain vitally important for drug discovery. Here we report that Pim kinases, in combination with DAPK3, regulate contractility and control hypertension. Using a co-crystal structure of lead molecule (HS38) in complex with DAPK3, a dual Pim/DAPK3 inhibitor (HS56) and selective DAPK3 inhibitors (HS94 and HS148) were developed to provide mechanistic insight into the polypharmacology of hypertension. In vitro and ex vivo studies indicated that Pim kinases directly phosphorylate smooth muscle targets and that Pim/DAPK3 inhibition, unlike selective DAPK3 inhibition, significantly reduces contractility. In vivo, HS56 decreased blood pressure in spontaneously hypertensive mice in a dose-dependent manner without affecting heart rate. These findings suggest including Pim kinase inhibition within a multi-target engagement strategy for hypertension management. HS56 represents a significant step in the development of molecularly targeted antihypertensive medications.

Systems biology network-based discovery of a small molecule activator BL-AD008 targeting AMPK/ZIPK and inducing apoptosis in cervical cancer

The aim of this study was to discover a small molecule activator BL-AD008 targeting AMPK/ZIPK and inducing apoptosis in cervical cancer. In this study, we systematically constructed the global protein-protein interaction (PPI) network and predicted apoptosis-related protein connections by the Naïve Bayesian model. Then, we identified some classical apoptotic PPIs and other previously unrecognized PPIs between apoptotic kinases, such as AMPK and ZIPK. Subsequently, we screened a series of candidate compounds targeting AMPK/ZIPK, synthesized some compounds and eventually discovered a novel dual-target activator (BL-AD008). Moreover, we found BL-AD008 bear remarkable anti-proliferative activities toward cervical cancer cells and could induce apoptosis by death-receptor and mitochondrial pathways. Additionally, we found that BL-AD008-induced apoptosis was affected by the combination of AMPK and ZIPK. Then, we found that BL-AD008 bear its anti-tumor activities and induced apoptosis by targeting AMPK/ZIPK in vivo. In conclusion, these results demonstrate the ability of systems biology network to identify some key apoptotic kinase targets AMPK and ZIPK; thus providing a dual-target small molecule activator (BL-AD008) as a potential new apoptosis-modulating drug in future cervical cancer therapy.