PF-431396

PF-431396 is a potent and highly selective pyrimidine-based inhibitor of both Pyk2 and FAK, Consistent with the idea that the tyrosine phosphorylation of Pyk2 and FAK involves an initial autophosphorylation or transphosphorylation step, treating A20 cells.

Focal adhesion kinases and calcium/calmodulin-dependent protein kinases regulate protein tyrosine phosphorylation in stallion sperm.[Pubmed:23595906]

Biol Reprod. 2013 Jun 6;88(6):138.

Protein tyrosine phosphorylation (PY) is a hallmark of sperm capacitation. In stallion sperm, calcium inhibits PY at pH <7.8, mediated by calmodulin. To explore the mechanism of that inhibition, we incubated stallion sperm in media without added calcium, with calcium, or with calcium plus the calmodulin inhibitor W-7 (Ca/W-7 treatment). Treatment with inhibitors of calcium/calmodulin-dependent kinases, protein kinase A (PRKA), or Src family kinases suppressed the PY induced by the absence of added calcium, but not that induced by the Ca/W-7 treatment, indicating that PY in the absence of added calcium occurred via the canonical PRKA pathway, but that PY in the Ca/W-7 treatment did not. This suggested that when calmodulin was inhibited, calcium stimulated PY via a noncanonical pathway. Incubation with PF-431396, an inhibitor of focal adhesion kinases (FAKs), a family of calcium-induced protein tyrosine kinases, inhibited the PY induced both by the absence of added calcium and by the Ca/W-7 treatment. Western blotting demonstrated that both FAK family members, protein tyrosine kinases 2 and 2B, were phosphorylated in the absence of added calcium and in the Ca/W-7 treatment, but not in the presence of calcium without calmodulin inhibitors. Inhibition of FAK proteins inhibited PY in stallion sperm incubated under capacitating conditions (in the presence of calcium, bovine serum albumin, and bicarbonate at pH >7.8). These results show for the first time a role for calcium/calmodulin-dependent kinases in PRKA-dependent sperm PY; a non-PRKA-dependent pathway regulating sperm PY; and the apparent involvement of the FAK family of protein tyrosine kinases downstream in both pathways.

The Pyk2/MCU pathway in the rat middle cerebral artery occlusion model of ischemic stroke.[Pubmed:28916471]

Neurosci Res. 2018 Jun;131:52-62.

Mitochondrial dysfunction caused by Ca(2+) overload plays an important role in ischemia-induced brain damage. Mitochondrial calcium uniporter (MCU), located on the mitochondrial inner membrane, is the major channel responsible for mitochondrial Ca(2+) uptake. Activated proline-rich tyrosine kinase 2 (Pyk2) can directly phosphorylate MCU, which enhances mitochondrial Ca(2+) uptake in cardiomyocytes. It has been suggested that the Pyk2/MCU pathway may be a novel therapeutic target in stress-induced cellular apoptosis. In this study, we explored the role of the Pyk2/MCU pathway in the ischemic brain following a stroke injury. We found that the Pyk2/MCU pathway is activated in a rat cerebral ischemia model, and is responsible for mitochondrial dysfunction and neuronal apoptosis. Inhibiting the Pyk2/MCU pathway with a Pyk2 inhibitor (PF-431396) prevented mitochondrial Ca(2+) overload, mitochondrial injury, proapoptotic protein release, and cell death. Interestingly, human urinary kallidinogenase (HUK) alleviated neuronal ischemic injury by inhibiting the Pyk2/MCU pathway, suggesting that the Pyk2/MCU pathway may be a protective target for ischemic stroke treatment.

Ganglioside GQ1b induces dopamine release through the activation of Pyk2.[Pubmed:26704905]

Mol Cell Neurosci. 2016 Mar;71:102-13.

Growing evidence indicates that GQ1b, one of the gangliosides members, contributes to synaptic transmission and synapse formation. Previous studies have shown that GQ1b could enhance depolarization induced neurotransmitter release, while the role of GQ1b in asynchronous release is still largely unknown. Here in our result, we found low concentration of GQ1b, but not GT1b or GD1b (which were generated from GQ1b by plasma membrane-associated sialidases), evoked asynchronous dopamine (DA) release from both clonal rat pheochromocytoma PC12 cells and rat striatal slices significantly. The release peaked at 2 min after GQ1b exposure, and lasted for more than 6 min. This effect was caused by the enhancement of intracellular Ca(2+) and the activation of Pyk2. Inhibition of Pyk2 by PF-431396 (a dual inhibitor of Pyk2 and FAK) or Pyk2 siRNA abolished DA release induced by GQ1b. Moreover, Pyk2 Y402, but not other tyrosine site, was phosphorylated at the peaking time. The mutant of Pyk2 Y402 (Pyk2-Y402F) was built to confirm the essential role of Y402 activation. Further studies revealed that activated Pyk2 stimulated ERK1/2 and p-38, while only the ERK1/2 activation was indispensable for GQ1b induced DA release, which interacted with Synapsin I directly and led to its phosphorylation, then depolymerization of F-actin, thus contributed to DA release. In conclusion, low concentration of GQ1b is able to enhance asynchronous DA release through Pyk2/ERK/Synapsin I/actin pathway. Our findings provide new insights into the role of GQ1b in neuronal communication, and implicate the potential application of GQ1b in neurological disorders.

NADPH oxidase/ROS-dependent PYK2 activation is involved in TNF-alpha-induced matrix metalloproteinase-9 expression in rat heart-derived H9c2 cells.[Pubmed:23774252]

Toxicol Appl Pharmacol. 2013 Oct 15;272(2):431-42.

TNF-alpha plays a mediator role in the pathogenesis of chronic heart failure contributing to cardiac remodeling and peripheral vascular disturbances. The implication of TNF-alpha in inflammatory responses has been shown to be mediated through up-regulation of matrix metalloproteinase-9 (MMP-9). However, the detailed mechanisms of TNF-alpha-induced MMP-9 expression in rat embryonic-heart derived H9c2 cells are largely not defined. We demonstrated that in H9c2 cells, TNF-alpha induced MMP-9 mRNA and protein expression associated with an increase in the secretion of pro-MMP-9. TNF-alpha-mediated responses were attenuated by pretreatment with the inhibitor of ROS (N-acetyl-l-cysteine, NAC), NADPH oxidase [apocynin (APO) or diphenyleneiodonium chloride (DPI)], MEK1/2 (U0126), p38 MAPK (SB202190), JNK1/2 (SP600125), NF-kappaB (Bay11-7082), or PYK2 (PF-431396) and transfection with siRNA of TNFR1, p47(phox), p42, p38, JNK1, p65, or PYK2. Moreover, TNF-alpha markedly induced NADPH oxidase-derived ROS generation in these cells. TNF-alpha-enhanced p42/p44 MAPK, p38 MAPK, JNK1/2, and NF-kappaB (p65) phosphorylation and in vivo binding of p65 to the MMP-9 promoter were inhibited by U0126, SB202190, SP600125, NAC, DPI, or APO. In addition, TNF-alpha-mediated PYK2 phosphorylation was inhibited by NAC, DPI, or APO. PYK2 inhibition could reduce TNF-alpha-stimulated MAPKs and NF-kappaB activation. Thus, in H9c2 cells, we are the first to show that TNF-alpha-induced MMP-9 expression is mediated through a TNFR1/NADPH oxidase/ROS/PYK2/MAPKs/NF-kappaB cascade. We demonstrated that NADPH oxidase-derived ROS generation is involved in TNF-alpha-induced PYK2 activation in these cells. Understanding the regulation of MMP-9 expression and NADPH oxidase activation by TNF-alpha on H9c2 cells may provide potential therapeutic targets of chronic heart failure.

A role for the tyrosine kinase Pyk2 in depolarization-induced contraction of vascular smooth muscle.[Pubmed:25713079]

J Biol Chem. 2015 Apr 3;290(14):8677-92.

Depolarization of the vascular smooth muscle cell membrane evokes a rapid (phasic) contractile response followed by a sustained (tonic) contraction. We showed previously that the sustained contraction involves genistein-sensitive tyrosine phosphorylation upstream of the RhoA/Rho-associated kinase (ROK) pathway leading to phosphorylation of MYPT1 (the myosin-targeting subunit of myosin light chain phosphatase (MLCP)) and myosin regulatory light chains (LC20). In this study, we addressed the hypothesis that membrane depolarization elicits activation of the Ca(2+)-dependent tyrosine kinase Pyk2 (proline-rich tyrosine kinase 2). Pyk2 was identified as the major tyrosine-phosphorylated protein in response to membrane depolarization. The tonic phase of K(+)-induced contraction was inhibited by the Pyk2 inhibitor sodium salicylate, which abolished the sustained elevation of LC20 phosphorylation. Membrane depolarization induced autophosphorylation (activation) of Pyk2 with a time course that correlated with the sustained contractile response. The Pyk2/focal adhesion kinase (FAK) inhibitor PF-431396 inhibited both phasic and tonic components of the contractile response to K(+), Pyk2 autophosphorylation, and LC20 phosphorylation but had no effect on the calyculin A (MLCP inhibitor)-induced contraction. Ionomycin, in the presence of extracellular Ca(2+), elicited a slow, sustained contraction and Pyk2 autophosphorylation, which were blocked by pre-treatment with PF-431396. Furthermore, the Ca(2+) channel blocker nifedipine inhibited peak and sustained K(+)-induced force and Pyk2 autophosphorylation. Inhibition of Pyk2 abolished the K(+)-induced translocation of RhoA to the particulate fraction and the phosphorylation of MYPT1 at Thr-697 and Thr-855. We conclude that depolarization-induced entry of Ca(2+) activates Pyk2 upstream of the RhoA/ROK pathway, leading to MYPT1 phosphorylation and MLCP inhibition. The resulting sustained elevation of LC20 phosphorylation then accounts for the tonic contractile response to membrane depolarization.

Structural characterization of proline-rich tyrosine kinase 2 (PYK2) reveals a unique (DFG-out) conformation and enables inhibitor design.[Pubmed:19244237]

J Biol Chem. 2009 May 8;284(19):13193-201.

Proline-rich tyrosine kinase 2 (PYK2) is a cytoplasmic, non-receptor tyrosine kinase implicated in multiple signaling pathways. It is a negative regulator of osteogenesis and considered a viable drug target for osteoporosis treatment. The high-resolution structures of the human PYK2 kinase domain with different inhibitor complexes establish the conventional bilobal kinase architecture and show the conformational variability of the DFG loop. The basis for the lack of selectivity for the classical kinase inhibitor, PF-431396, within the FAK family is explained by our structural analyses. Importantly, the novel DFG-out conformation with two diarylurea inhibitors (BIRB796, PF-4618433) reveals a distinct subclass of non-receptor tyrosine kinases identifiable by the gatekeeper Met-502 and the unique hinge loop conformation of Leu-504. This is the first example of a leucine residue in the hinge loop that blocks the ATP binding site in the DFG-out conformation. Our structural, biophysical, and pharmacological studies suggest that the unique features of the DFG motif, including Leu-504 hinge-loop variability, can be exploited for the development of selective protein kinase inhibitors.

Proline-rich tyrosine kinase 2 regulates osteoprogenitor cells and bone formation, and offers an anabolic treatment approach for osteoporosis.[Pubmed:17537919]

Proc Natl Acad Sci U S A. 2007 Jun 19;104(25):10619-24.

Bone is accrued and maintained primarily through the coupled actions of bone-forming osteoblasts and bone-resorbing osteoclasts. Cumulative in vitro studies indicated that proline-rich tyrosine kinase 2 (PYK2) is a positive mediator of osteoclast function and activity. However, our investigation of PYK2-/- mice did not reveal evidence supporting an essential function for PYK2 in osteoclasts either in vivo or in culture. We find that PYK2-/- mice have high bone mass resulting from an unexpected increase in bone formation. Consistent with the in vivo findings, mouse bone marrow cultures show that PYK2 deficiency enhances differentiation and activity of osteoprogenitor cells, as does expressing a PYK2-specific short hairpin RNA or dominantly interfering proteins in human mesenchymal stem cells. Furthermore, the daily administration of a small-molecule PYK2 inhibitor increases bone formation and protects against bone loss in ovariectomized rats, an established preclinical model of postmenopausal osteoporosis. In summary, we find that PYK2 regulates the differentiation of early osteoprogenitor cells across species and that inhibitors of the PYK2 have potential as a bone anabolic approach for the treatment of osteoporosis.

PF-431396 is dual focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2) inhibitor (IC50 values are 2 and 11 nM respectively), PF-431396 has a Kd value of 445 nM for BRD4.

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