Mechanism of inhibition of P-glycoprotein-mediated drug transport by protein kinase C blockers

Ariel F. Castro; Julie K. Horton; Carlos G. Vanoye; Guillermo A. Altenberg

doi:10.1016/S0006-2952(99)00288-9

Mechanism of inhibition of P-glycoprotein-mediated drug transport by protein kinase C blockers

Ariel F. Castro, Julie K. Horton, Carlos G. Vanoye, Guillermo A. Altenberg^*

^*Corresponding author for this work

Pharmacology

Research output: Contribution to journal › Article › peer-review

43 Scopus citations

Abstract

P-glycoprotein is a membrane ATPase that transports drugs out of cells and confers resistance to a variety of chemically unrelated drugs (multidrug resistance). P-glycoprotein is phosphorylated by protein kinase C (PKC), and PKC blockers reduce P-glycoprotein phosphorylation and increase drug accumulation. These observations suggest that phosphorylation of P- glycoprotein stimulates drug transport. However, there is evidence that PKC inhibitors directly interact with P-glycoprotein, and therefore the mechanism of their effects on P-glycoprotein-mediated drug transport and the possible role of phosphorylation in the regulation of P-glycoprotein function remain unclear. In the present work, we studied the effects of different kinds of PKC inhibitors on drug transport in cells expressing wild-type human P- glycoprotein and a PKC phosphorylation-defective mutant. We demonstrated that PKC blockers inhibit drug transport by mechanisms independent of P- glycoprotein phosphorylation. Inhibition by the blockers occurs by (i) direct competition with transported drugs for binding to P-glycoprotein, and (ii) indirect inhibition through a pathway that involves PKC inhibition, but is independent of P-glycoprotein phosphorylation. The effects of the blockers on P-glycoprotein phosphorylation do not seem to play an important role, but the PKC-signaling pathway regulates P-glycoprotein-mediated drug transport.

Original language	English (US)
Pages (from-to)	1723-1733
Number of pages	11
Journal	Biochemical Pharmacology
Volume	58
Issue number	11
DOIs	https://doi.org/10.1016/S0006-2952(99)00288-9
State	Published - Dec 1 1999

Funding

We thank Drs. S. Weinman and J-T. Zhang for comments on a preliminary version of the manuscript, and Dr. P. Melera for providing us with the mammalian expression vector pLK-444. We also wish to thank J. Ehardt, J. Lock, and Dr. C. Wang for technical assistance, and M. Griffin for the flow cytometry studies performed at the Flow Cytometry and Cell Sorting Facility of the University of Texas Medical Branch. We appreciate the work of Dr. T. Pourcher in the engineering of the polyhistidine tag at the C-terminal end of the MDR1 cDNA constructs. This work was supported, in part, by American Heart Association, Texas Affiliate, Inc., Grant 96G-1613, National Cancer Institute Grant CA72783, and National Institutes of Diabetes and Kidney Diseases Grant DK-08865.

Keywords

ABC proteins
Chelerythrine
MDR1
Multidrug resistance
Phosphorylation
Safingol

ASJC Scopus subject areas

Biochemistry
Pharmacology

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10.1016/S0006-2952(99)00288-9

Cite this

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title = "Mechanism of inhibition of P-glycoprotein-mediated drug transport by protein kinase C blockers",

abstract = "P-glycoprotein is a membrane ATPase that transports drugs out of cells and confers resistance to a variety of chemically unrelated drugs (multidrug resistance). P-glycoprotein is phosphorylated by protein kinase C (PKC), and PKC blockers reduce P-glycoprotein phosphorylation and increase drug accumulation. These observations suggest that phosphorylation of P- glycoprotein stimulates drug transport. However, there is evidence that PKC inhibitors directly interact with P-glycoprotein, and therefore the mechanism of their effects on P-glycoprotein-mediated drug transport and the possible role of phosphorylation in the regulation of P-glycoprotein function remain unclear. In the present work, we studied the effects of different kinds of PKC inhibitors on drug transport in cells expressing wild-type human P- glycoprotein and a PKC phosphorylation-defective mutant. We demonstrated that PKC blockers inhibit drug transport by mechanisms independent of P- glycoprotein phosphorylation. Inhibition by the blockers occurs by (i) direct competition with transported drugs for binding to P-glycoprotein, and (ii) indirect inhibition through a pathway that involves PKC inhibition, but is independent of P-glycoprotein phosphorylation. The effects of the blockers on P-glycoprotein phosphorylation do not seem to play an important role, but the PKC-signaling pathway regulates P-glycoprotein-mediated drug transport.",

keywords = "ABC proteins, Chelerythrine, MDR1, Multidrug resistance, Phosphorylation, Safingol",

author = "Castro, {Ariel F.} and Horton, {Julie K.} and Vanoye, {Carlos G.} and Altenberg, {Guillermo A.}",

note = "Funding Information: We thank Drs. S. Weinman and J-T. Zhang for comments on a preliminary version of the manuscript, and Dr. P. Melera for providing us with the mammalian expression vector pLK-444. We also wish to thank J. Ehardt, J. Lock, and Dr. C. Wang for technical assistance, and M. Griffin for the flow cytometry studies performed at the Flow Cytometry and Cell Sorting Facility of the University of Texas Medical Branch. We appreciate the work of Dr. T. Pourcher in the engineering of the polyhistidine tag at the C-terminal end of the MDR1 cDNA constructs. This work was supported, in part, by American Heart Association, Texas Affiliate, Inc., Grant 96G-1613, National Cancer Institute Grant CA72783, and National Institutes of Diabetes and Kidney Diseases Grant DK-08865.",

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AU - Castro, Ariel F.

AU - Horton, Julie K.

AU - Vanoye, Carlos G.

AU - Altenberg, Guillermo A.

N1 - Funding Information: We thank Drs. S. Weinman and J-T. Zhang for comments on a preliminary version of the manuscript, and Dr. P. Melera for providing us with the mammalian expression vector pLK-444. We also wish to thank J. Ehardt, J. Lock, and Dr. C. Wang for technical assistance, and M. Griffin for the flow cytometry studies performed at the Flow Cytometry and Cell Sorting Facility of the University of Texas Medical Branch. We appreciate the work of Dr. T. Pourcher in the engineering of the polyhistidine tag at the C-terminal end of the MDR1 cDNA constructs. This work was supported, in part, by American Heart Association, Texas Affiliate, Inc., Grant 96G-1613, National Cancer Institute Grant CA72783, and National Institutes of Diabetes and Kidney Diseases Grant DK-08865.

PY - 1999/12/1

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N2 - P-glycoprotein is a membrane ATPase that transports drugs out of cells and confers resistance to a variety of chemically unrelated drugs (multidrug resistance). P-glycoprotein is phosphorylated by protein kinase C (PKC), and PKC blockers reduce P-glycoprotein phosphorylation and increase drug accumulation. These observations suggest that phosphorylation of P- glycoprotein stimulates drug transport. However, there is evidence that PKC inhibitors directly interact with P-glycoprotein, and therefore the mechanism of their effects on P-glycoprotein-mediated drug transport and the possible role of phosphorylation in the regulation of P-glycoprotein function remain unclear. In the present work, we studied the effects of different kinds of PKC inhibitors on drug transport in cells expressing wild-type human P- glycoprotein and a PKC phosphorylation-defective mutant. We demonstrated that PKC blockers inhibit drug transport by mechanisms independent of P- glycoprotein phosphorylation. Inhibition by the blockers occurs by (i) direct competition with transported drugs for binding to P-glycoprotein, and (ii) indirect inhibition through a pathway that involves PKC inhibition, but is independent of P-glycoprotein phosphorylation. The effects of the blockers on P-glycoprotein phosphorylation do not seem to play an important role, but the PKC-signaling pathway regulates P-glycoprotein-mediated drug transport.

AB - P-glycoprotein is a membrane ATPase that transports drugs out of cells and confers resistance to a variety of chemically unrelated drugs (multidrug resistance). P-glycoprotein is phosphorylated by protein kinase C (PKC), and PKC blockers reduce P-glycoprotein phosphorylation and increase drug accumulation. These observations suggest that phosphorylation of P- glycoprotein stimulates drug transport. However, there is evidence that PKC inhibitors directly interact with P-glycoprotein, and therefore the mechanism of their effects on P-glycoprotein-mediated drug transport and the possible role of phosphorylation in the regulation of P-glycoprotein function remain unclear. In the present work, we studied the effects of different kinds of PKC inhibitors on drug transport in cells expressing wild-type human P- glycoprotein and a PKC phosphorylation-defective mutant. We demonstrated that PKC blockers inhibit drug transport by mechanisms independent of P- glycoprotein phosphorylation. Inhibition by the blockers occurs by (i) direct competition with transported drugs for binding to P-glycoprotein, and (ii) indirect inhibition through a pathway that involves PKC inhibition, but is independent of P-glycoprotein phosphorylation. The effects of the blockers on P-glycoprotein phosphorylation do not seem to play an important role, but the PKC-signaling pathway regulates P-glycoprotein-mediated drug transport.

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KW - Phosphorylation

KW - Safingol

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Mechanism of inhibition of P-glycoprotein-mediated drug transport by protein kinase C blockers

Abstract

Funding

Keywords

ASJC Scopus subject areas

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