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H. A. Pereira, S. Logan, M. L. Gonzalez, J. Chodosh; Protein Kinase C (PKC) Activation Is Required for Migration of Human Corneal Epithelial Cells (HCEC) in Response to CAP37, a Multifunctional Neutrophil-Derived Inflammatory Protein. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2379.
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CAP37, is an inflammatory mediator that is constitutively expressed in neutrophils and plays a critical role in the innate defenses of the host. Prior studies from our laboratory had demonstrated that CAP37 had significant regulatory effects on various HCEC functions including migration. However, the molecular mechanism(s) by which CAP37 mediates these functions is still unknown. The purpose of these studies was to evaluate the signal transduction pathways involved in CAP37-mediated HCEC migration.
Immortalized HCEC were treated with pharmacological inhibitors specific for PKC, which included Ro-318220 (10 nM), calphostin C (50 nM), and Bisindolylmaleimide I/GF 109203X/Gö6850 (100 nM) for 15 and 60 min. The HCEC were then compared for extent of migration toward CAP37 (1000 ng/ml) and platelet-derived growth factor (PDGF, 20 ng/ml), a known chemoattractant for HCEC, at 4 hr using the modified Boyden Chemotaxis chamber assay. To further investigate potential signaling molecules in CAP37-mediated migration we studied the chemotactic response of HCEC toward PDGF and CAP37 in the presence PD-98059 (2 µM), a MAP kinase kinase (MEK1) inhibitor, SP600125 (40 nM) an inhibitor of c-Jun N-terminal kinase (JNK), and SB203580 (34 nM) an inhibitor of p38 kinase. HCEC were also treated with HA-1004 and H-89, inhibitors of protein kinase A (PKA). Chemotaxis of HCEC was performed following PKC depletion with phorbol-12, 13-dibutyrate (PDBu). Western blots were performed on HCEC extracts to determine the identity of the PKC isoforms involved.
HCEC migration was inhibited by 90% following treatment at 60 min with the PKC inhibitors Ro-31-8220 and calphostin C. However, Bisindolylmaleimide I was not as effective, resulting in approximately 55% inhibition under the conditions stated. Other inhibitors tested indicated a lack of attenuation of the chemotactic response suggesting that they were not involved in CAP37-mediated HCEC migration. Both CAP37 and PDGF were unable to support migration of HCEC in which PKC had been depleted following chronic exposure to PDBu. Western blot analysis suggested that PKC isoforms alpha, delta, and or epsilon are likely involved.
These findings taken together strongly suggest that PKC is involved in CAP37-mediated HCEC migration.
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