Protein kinase C activation induces phosphatidylserine exposure on red blood cells

Kitty De Jong, Michael P. Rettig, Philip S. Low, Frans A. Kuypers

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

We have shown previously that red blood cells (RBCs) can be induced to influx Ca2+ when treated with lipid mediators, such as lysophosphatidic acid and prostaglandin E2, that are released during clot formation. Since calcium loading of RBCs can lead to both protein kinase C (PKC) activation and phosphatidylserine (PS) exposure, we decided to investigate the possible linkage between PKC activation and membrane PS scrambling using phorbol 12-myristate-13-acetate (PMA), a commonly used activator of PKC. Treatment of RBCs with PMA in a calcium-containing buffer caused immediate PS exposure in an RBC subpopulation. The size of the subpopulation did not change upon further incubation, indicating that not all RBCs are equally susceptible to this treatment. Using a fluorescent indicator, we found a subpopulation of RBCs with elevated intracellular calcium levels. In the absence of extracellular calcium, no PS exposure was found. However, we did find cells with high levels of calcium that did not expose PS, and a variable percentage of PS-exposing cells that did not show elevated calcium concentrations. Inhibition of PKC with either calphostin C, a blocker of the PMA binding site, or chelerythrine chloride, an inhibitor of the active site, diminished the level of formation of PS-exposing cells. However, the inhibitors had different effects on calcium internalization, indicating that a high calcium concentration alone was not responsible for inducing PS exposure in the absence of PKC activity. Moreover, PKC inhibition could prevent PS exposure induced by calcium and ionophore treatment of RBCs. We conclude that PKC is implicated in the mechanism of membrane phospholipid scrambling.

Original languageEnglish
Pages (from-to)12562-12567
Number of pages6
JournalBiochemistry
Volume41
Issue number41
DOIs
StatePublished - Oct 15 2002
Externally publishedYes

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