Biochemical and Biophysical Research Communications
Protein kinase C β and δ isoenzymes mediate cholesterol accumulation in PMA-activated macrophages
Section snippets
Materials and methods
PKC inhibitors. PKC pseudosubstrate myristoylated peptide inhibitors for α + β (P-205) and ε (P-223), HBDDE, RO 32-0432, Go6976, and Go6983 were obtained from Biomol. PKC pseudosubstrate myristoylated peptide inhibitors for theta (#539636) and eta (#539602) and Go6850 were obtained from Calbiochem. LY333531 was obtained from Alexis. The non-PKC inhibitors genistein and H89 were obtained from Biomol.
Culture of human monocyte-derived macrophages. Human monocytes were purified with counterflow
Kinase dependency of PMA-stimulated macrophage cholesterol accumulation
Previously we showed that PMA-stimulated macrophage cholesterol accumulation during incubation with native LDL could be inhibited with broad specificity PKC inhibitors [6]. To learn whether other protein kinase classes functioned in PMA-stimulated cholesterol accumulation we tested the effects of genistein, a pan tyrosine kinase inhibitor, and HA89, a cyclic AMP-dependent protein kinase (PKA) inhibitor, on this process. Neither of these protein kinase inhibitors significantly decreased
Discussion
Macrophage foam cell formation has been thought to occur only by receptor-mediated uptake of modified LDL. We recently showed that PMA-activated macrophages take up native LDL through receptor-independent fluid-phase macropinocytosis and form foam cells due to massive accumulation of LDL-derived cholesterol [6], [7]. In this report, we have identified β and some additional PKC isoenzyme, most likely δ, as mediators of PMA-stimulated macrophage cholesterol accumulation. These two PKC isoenzymes
Acknowledgment
We thank Rani Rao for technical assistance, and the Department of Transfusion Medicine, Clinical Center, National Institutes of Health, for providing elutriated monocytes. This research was supported in part by the Intramural Research Program of the NIH, NHLBI.
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