@article{eckert_sharief_jones_2009, title={p38 mitogen-activated kinase (MAPK) is essential for equine neutrophil migration}, volume={129}, ISSN={["1873-2534"]}, url={http://europepmc.org/abstract/med/19095309}, DOI={10.1016/j.vetimm.2008.11.007}, abstractNote={Equine laminar tissues do not contain resident neutrophils and have less superoxide dismutase (SOD) activity than other equine tissues, which makes them inherently more vulnerable to damage induced by reactive oxygen species (ROS) produced by neutrophils that enter the tissues. In the advanced clinical stages of acute laminitis, pathologic events in affected feet include a breakdown in the basement membrane, neutrophil infiltration, and platelet-neutrophil aggregates in laminar dermal veins, highlighting the contribution of neutrophils to the pathophysiology of the disease. The aim of this study was to determine the role of p38 MAPK in the mechanism underlying equine neutrophil migration to potentially reveal therapeutic targets that may limit lamellar damage from the neutrophil influx that occurs in acute laminitis. We determined that the endogenous chemoattractant LTB(4) transiently activated p38 MAPK and induced chemotaxis of equine primary neutrophils. Inhibition with the p38 MAPK specific inhibitor SB203580 reduced LTB(4)-induced migration in a dose-dependent manner with an IC(50) of 2.8 microM. We then examined the potential mechanisms underlying the ability of SB203580 to abolish migration. We determined that inhibition of p38 MAPK with 10 microM SB203580 disrupted the ability of neutrophils to polarize in response to LTB(4) and PAF. In contrast, p38 MAPK did not appear to be required for chemoattractant- or PKC-induced beta2 integrin-dependent adhesion or chemoattractant-induced upregulation of surface beta2 integrins, but was required for TNFalpha-induced adhesion. These findings support a function for p38 MAPK in equine neutrophil migration and suggest the potential for the ability of p38 MAPK inhibition to limit neutrophilic inflammation in the laminae during acute laminitis.}, number={3-4}, journal={VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY}, author={Eckert, Rachael E. and Sharief, Yousuf and Jones, Samuel L.}, year={2009}, month={Jun}, pages={181–191} }
 @article{chilcoat_sharief_jones_2008, title={Tonic protein kinase A activity maintains inactive beta 2 integrins in unstimulated neutrophils by reducing myosin light-chain phosphorylation: role of myosin light-chain kinase and Rho kinase}, volume={83}, ISSN={["0741-5400"]}, url={http://europepmc.org/abstract/med/18218860}, DOI={10.1189/jlb.0405192}, abstractNote={AbstractActivation of β2 integrins is necessary for neutrophil adhesion and full activation of neutrophil effector functions. We demonstrated previously that inhibition of protein kinase A (PKA) activity in quiescent neutrophils is sufficient to increase β2-integrin cell surface expression, affinity, and adhesion. Thus, a tonic level of PKA activity prevents inappropriate activation of β2 integrins in unstimulated neutrophils. Myosin light-chain (MLC) phosphorylation is an important regulator of leukocyte integrin function and adhesion. Moreover, PKA regulates MLC phosphorylation via inhibiting MLC kinase (MLCK) and MLC dephosphorylation via effects on the Rho kinase (ROCK)/MLC phosphatase pathway. We hypothesize that the tonic inhibitory effect of PKA on β2-integrin activation neutrophils operates via its inhibition of MLC phosphorylation. We demonstrate here that inhibition of PKA activity with KT5720 activated β2 integrins and adhesion coincident with an increase in MLC serine 19 (Ser 19) phosphorylation. KT5720-induced activation of β2 integrins, adhesion, and MLC Ser 19 phosphorylation was abolished by pretreatment with the MLCK inhibitor ML-7 and specific MLCK inhibitory peptides but not the ROCK inhibitor Y-27632. These findings demonstrate that tonic PKA activity prevents activation of β2 integrins and adhesion by inhibiting MLC phosphorylation via a MLCK-dependent but ROCK-independent pathway.}, number={4}, journal={JOURNAL OF LEUKOCYTE BIOLOGY}, author={Chilcoat, Clayton D. and Sharief, Yousuf and Jones, Samuel L.}, year={2008}, month={Apr}, pages={964–971} }
 @article{green_eckert_sharief_crews_adler_jones_2007, title={A peptide against the N-terminus of MARCKS protein attenuates leukocyte migration.}, volume={175}, journal={404nOtfound}, author={Green, T. D. and Eckert, B. S. and Sharief, Y. and Crews, A. L. and Adler, K. B. and Jones, S. L.}, year={2007}, pages={A915} }
 @article{jones_sharief_2005, title={Asymmetrical protein kinase A activity establishes neutrophil cytoskeletal polarity and enables chemotaxis}, volume={78}, ISSN={["1938-3673"]}, url={http://europepmc.org/abstract/med/15817703}, DOI={10.1189/jlb.0804459}, abstractNote={AbstractNeutrophil chemotaxis requires precise spatial organization of the actin cytoskeleton and integrin activation to polarize the cell and enable migration. Protein kinase A (PKA) activity regulates integrin activation and actin cytoskeletal organization, suggesting that PKA is a key element in the mechanism regulating neutrophil chemotaxis. Our hypothesis is that asymmetrical PKA activity is critical for establishing neutrophil adhesive and cytoskeletal polarity required for migration during chemotaxis. To test this hypothesis, we first determined that global treatment with the PKA inhibitor KT5720 decreased formylated Met-Leu-Phe (fMLF)-induced migration. The ability of PKA inhibitors to reduce migration correlated with increased overall β2 integrin cell-surface expression, affinity activation, and cellular adhesion. We next determined whether asymmetrical PKA activity was sufficient to induce migration. Exposure to gradient of the PKA inhibitors KT5720 or H-89 or a stearated, cell-permeant peptide (St-Ht31), which inhibits PKA binding to anchorage proteins, stimulated neutrophil migration in a chemotaxis chamber. Global treatment with KT5720 abolished the ability of fMLF to polarize the neutrophil actin cytoskeleton. In contrast to global treatment with KT5720, a point source of KT5720 was sufficient to polarize the actin cytoskeleton. The ability of KT5720 and St-Ht31 to stimulate migration was abolished by pretreatment with the phosphatidylinositol-3 kinase (PI-3K) inhibitors wortmannin and LY294002. These data suggest that asymmetrical PKA activity is necessary and sufficient for actin cytoskeletal polarization and migration during neutrophil chemotaxis. In addition, our data suggest PI-3K is an effector of PKA during chemotaxis.}, number={1}, journal={JOURNAL OF LEUKOCYTE BIOLOGY}, author={Jones, SL and Sharief, Y}, year={2005}, month={Jul}, pages={248–258} }