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Pourmal S, Green E, Bajaj R, Chemmama IE, Knudsen GM, Gupta M, Sali A, Cheng Y, Craik CS, Kroetz DL, Stroud RM. Structural basis of prostaglandin efflux by MRP4. Nat Struct Mol Biol 2024; 31:621-632. [PMID: 38216659 PMCID: PMC11145372 DOI: 10.1038/s41594-023-01176-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 11/07/2023] [Indexed: 01/14/2024]
Abstract
Multidrug resistance protein 4 (MRP4) is a broadly expressed ATP-binding cassette transporter that is unique among the MRP subfamily for transporting prostanoids, a group of signaling molecules derived from unsaturated fatty acids. To better understand the basis of the substrate selectivity of MRP4, we used cryogenic-electron microscopy to determine six structures of nanodisc-reconstituted MRP4 at various stages throughout its transport cycle. Substrate-bound structures of MRP4 in complex with PGE1, PGE2 and the sulfonated-sterol DHEA-S reveal a common binding site that accommodates a diverse set of organic anions and suggest an allosteric mechanism for substrate-induced enhancement of MRP4 ATPase activity. Our structure of a catalytically compromised MRP4 mutant bound to ATP-Mg2+ is outward-occluded, a conformation previously unobserved in the MRP subfamily and consistent with an alternating-access transport mechanism. Our study provides insights into the endogenous function of this versatile efflux transporter and establishes a basis for MRP4-targeted drug design.
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Affiliation(s)
- Sergei Pourmal
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
- Program in Chemistry and Chemical Biology, University of California, San Francisco, CA, USA
- Genentech, South San Francisco, CA, USA
| | - Evan Green
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
- Biophysics Graduate Program, University of California, San Francisco, CA, USA
- Exelixis, Alameda, CA, USA
| | - Ruchika Bajaj
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA
| | - Ilan E Chemmama
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA
- Brightseed, South San Francisco, CA, USA
| | - Giselle M Knudsen
- Quantitative Biosciences Institute, University of California, San Francisco, CA, USA
| | - Meghna Gupta
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA
- Quantitative Biosciences Institute, University of California, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Yifan Cheng
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, CA, USA
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Deanna L Kroetz
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA.
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA.
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Misoprostol treatment prevents hypoxia-induced cardiac dysfunction through a 14-3-3 and PKA regulatory motif on Bnip3. Cell Death Dis 2021; 12:1105. [PMID: 34824192 PMCID: PMC8617186 DOI: 10.1038/s41419-021-04402-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 11/01/2021] [Accepted: 11/09/2021] [Indexed: 12/31/2022]
Abstract
Systemic hypoxia is a common element in most perinatal emergencies and is a known driver of Bnip3 expression in the neonatal heart. Bnip3 plays a prominent role in the evolution of necrotic cell death, disrupting ER calcium homeostasis and initiating mitochondrial permeability transition (MPT). Emerging evidence suggests a cardioprotective role for the prostaglandin E1 analog misoprostol during periods of hypoxia, but the mechanisms for this protection are not completely understood. Using a combination of mouse and cell models, we tested if misoprostol is cardioprotective during neonatal hypoxic injury by altering Bnip3 function. Here we report that hypoxia elicits mitochondrial-fragmentation, MPT, reduced ejection fraction, and evidence of necroinflammation, which were abrogated with misoprostol treatment or Bnip3 knockout. Through molecular studies we show that misoprostol leads to PKA-dependent Bnip3 phosphorylation at threonine-181, and subsequent redistribution of Bnip3 from mitochondrial Opa1 and the ER through an interaction with 14-3-3 proteins. Taken together, our results demonstrate a role for Bnip3 phosphorylation in the regulation of cardiomyocyte contractile/metabolic dysfunction, and necroinflammation. Furthermore, we identify a potential pharmacological mechanism to prevent neonatal hypoxic injury.
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