Browsing by Subject "Tyrosine kinase"

Now showing 1 - 3 of 3
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    Dynamin and PTP-PEST cooperatively regulate Pyk2 dephosphorylation in osteoclasts
    (2012-05) Eleniste, Pierre P; Du, Liping; Shivanna, Mahesh; Bruzzaniti, Angela
    Bone loss is caused by the dysregulated activity of osteoclasts which degrade the extracellular bone matrix. The tyrosine kinase Pyk2 is highly expressed in osteoclasts, and mice lacking Pyk2 exhibit an increase in bone mass, in part due to impairment of osteoclast function. Pyk2 is activated by phosphorylation at Y402 following integrin activation, but the mechanisms leading to Pyk2 dephosphorylation are poorly understood. In the current study, we examined the mechanism of action of the dynamin GTPase on Pyk2 dephosphorylation. Our studies reveal a novel mechanism for the interaction of Pyk2 with dynamin, which involves the binding of Pyk2's FERM domain with dynamin's plextrin homology domain. In addition, we demonstrate that the dephosphorylation of Pyk2 requires dynamin's GTPase activity and is mediated by the tyrosine phosphatase PTP-PEST. The dephosphorylation of Pyk2 by dynamin and PTP-PEST may be critical for terminating outside-in integrin signaling, and for stabilizing cytoskeletal reorganization during osteoclast bone resorption.
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    Inhibition of Lyn kinase: A novel approach to treatment of Alzheimer’s disease
    (Wiley, 2025-01-09) Benitah, Avi L.; Richardson, Timothy I.; Weerawarna, Pathum M.; Robo, Michael T.; Mason, Emily R.; Pharmacology and Toxicology, School of Medicine
    Background: The TREAT‐AD centers aim to improve Alzheimer’s Disease (AD) research by offering free, high‐quality tools and technologies. Lyn is a tyrosine kinase that belongs to the Src family kinases. The expression of Lyn and its activity have been implicated in AD. This class of proteins is involved in TREM2 mediated microglial activation and phagocytosis, a process which is beneficial for clearing neurotoxins such as Aβ oligomers in the brain. Lyn inhibition may activate microglia. Given the relationship between accumulation of Aβ and its exacerbation of neurodegenerative diseases such as AD, selective inhibition of Lyn has been proposed as a novel therapeutic approach to treating early‐onset AD. However, potent, selective, and brain penetrant Lyn inhibitors are unavailable to test this hypothesis. Method: We screened a variety of known kinase inhibitors to determine their activity towards inhibition of Lyn using the biochemical HotSpot kinase assay. With this data in hand, we identified imatinib as a starting point for the design of novel Lyn inhibitors. Structure‐based design and computational docking models were used to propose more active and selective Lyn inhibitors, which were synthesized. The activities were determined, and multiple parameter optimization (MPO) informed iterative Structure Activity Relationship (SAR) studies. The best compounds were evaluated in assays of microglia activation, and their drug metabolism and pharmacokinetic (DMPK) properties were determined. Result: A series of novel type II inhibitors are now available for testing. The results demonstrate a unique tail group provides the novel scaffold with potent activity and selectivity towards inhibition of Lyn, exceeding that of imatinib. Conclusion: Computational models, SAR, and MPO provided potent and selective Lyn inhibitors with good DMPK properties. Further studies are under way to determine the impact of these compounds on TREM2 mediated activation of microglia both in vitro and in vivo.
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    Pyk2 and Megakaryocytes Regulate Osteoblast Differentiation and Migration Via Distinct and Overlapping Mechanisms
    (Wiley, 2016-06) Eleniste, Pierre P.; Patel, Vruti; Posritong, Sumana; Zero, Odette; Largura, Heather; Cheng, Ying-Hua; Himes, Evan R.; Hamilton, Matthew; Baughman, Jenna; Kacena, Melissa A.; Bruzzaniti, Angela; Department of Biomedical and Applied Sciences, School of Dentistry
    Osteoblast differentiation and migration are necessary for bone formation during bone remodeling. Mice lacking the proline-rich tyrosine kinase Pyk2 (Pyk2-KO) have increased bone mass, in part due to increased osteoblast proliferation. Megakaryocytes (MKs), the platelet-producing cells, also promote osteoblast proliferation in vitro and bone-formation in vivo via a pathway that involves Pyk2. In the current study, we examined the mechanism of action of Pyk2, and the role of MKs, on osteoblast differentiation and migration. We found that Pyk2-KO osteoblasts express elevated alkaline phosphatase (ALP), type I collagen and osteocalcin mRNA levels as well as increased ALP activity, and mineralization, confirming that Pyk2 negatively regulates osteoblast function. Since Pyk2 Y402 phosphorylation is important for its catalytic activity and for its protein-scaffolding functions, we expressed the phosphorylation-mutant (Pyk2(Y402F) ) and kinase-mutant (Pyk2(K457A) ) in Pyk2-KO osteoblasts. Both Pyk2(Y402F) and Pyk2(K457A) reduced ALP activity, whereas only kinase-inactive Pyk2(K457A) inhibited Pyk2-KO osteoblast migration. Consistent with a role for Pyk2 on ALP activity, co-culture of MKs with osteoblasts led to a decrease in the level of phosphorylated Pyk2 (pY402) as well as a decrease in ALP activity. Although, Pyk2-KO osteoblasts exhibited increased migration compared to wild-type osteoblasts, Pyk2 expression was not required necessary for the ability of MKs to stimulate osteoblast migration. Together, these data suggest that osteoblast differentiation and migration are inversely regulated by MKs via distinct Pyk2-dependent and independent signaling pathways. Novel drugs that distinguish between the kinase-dependent or protein-scaffolding functions of Pyk2 may provide therapeutic specificity for the control of bone-related diseases.