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Peters CH, Singh RK, Langley AA, Nichols WG, Ferris HR, Jeffrey DA, Proenza C, Bankston JR. LRMP inhibits cAMP potentiation of HCN4 channels by disrupting intramolecular signal transduction. eLife 2024; 12:RP92411. [PMID: 38652113 PMCID: PMC11037915 DOI: 10.7554/elife.92411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024] Open
Abstract
Lymphoid restricted membrane protein (LRMP) is a specific regulator of the hyperpolarization-activated cyclic nucleotide-sensitive isoform 4 (HCN4) channel. LRMP prevents cAMP-dependent potentiation of HCN4, but the interaction domains, mechanisms of action, and basis for isoform-specificity remain unknown. Here, we identify the domains of LRMP essential for this regulation, show that LRMP acts by disrupting the intramolecular signal transduction between cyclic nucleotide binding and gating, and demonstrate that multiple unique regions in HCN4 are required for LRMP isoform-specificity. Using patch clamp electrophysiology and Förster resonance energy transfer (FRET), we identified the initial 227 residues of LRMP and the N-terminus of HCN4 as necessary for LRMP to associate with HCN4. We found that the HCN4 N-terminus and HCN4-specific residues in the C-linker are necessary for regulation of HCN4 by LRMP. Finally, we demonstrated that LRMP-regulation can be conferred to HCN2 by addition of the HCN4 N-terminus along with mutation of five residues in the S5 region and C-linker to the cognate HCN4 residues. Taken together, these results suggest that LRMP inhibits HCN4 through an isoform-specific interaction involving the N-terminals of both proteins that prevents the transduction of cAMP binding into a change in channel gating, most likely via an HCN4-specific orientation of the N-terminus, C-linker, and S4-S5 linker.
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Affiliation(s)
- Colin H Peters
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - Rohit K Singh
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
- Skaggs School of Pharmacy, Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - Avery A Langley
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - William G Nichols
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - Hannah R Ferris
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - Danielle A Jeffrey
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
- Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical CampusAuroraUnited States
| | - John R Bankston
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical CampusAuroraUnited States
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Peters CH, Singh RK, Langley AA, Nichols WG, Ferris HR, Jeffrey DA, Proenza C, Bankston JR. LRMP inhibits cAMP potentiation of HCN4 channels by disrupting intramolecular signal transduction. bioRxiv 2024:2023.08.29.555242. [PMID: 37693562 PMCID: PMC10491135 DOI: 10.1101/2023.08.29.555242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Lymphoid restricted membrane protein (LRMP) is a specific regulator of the hyperpolarization-activated cyclic nucleotide-sensitive isoform 4 (HCN4) channel. LRMP prevents cAMP-dependent potentiation of HCN4 but the interaction domains, mechanisms of action, and basis for isoform-specificity remain unknown. Here we identify the domains of LRMP essential for regulation. We show that LRMP acts by disrupting the intramolecular signal transduction between cyclic nucleotide binding and gating. And we demonstrate that multiple unique regions in HCN4 are required for LRMP isoform-specificity. Using patch clamp electrophysiology and Förster resonance energy transfer (FRET), we showed that the initial 227 residues of LRMP and the N-terminus of HCN4 are necessary for LRMP to interact with HCN4. We found that the HCN4 N-terminus and HCN4-specific residues in the C-linker are necessary for regulation of HCN4 by LRMP. And we demonstrate that LRMP-regulation can be conferred to HCN2 by addition of the HCN4 N-terminus along with mutation of 5 residues in the S5 region and C-linker to the cognate HCN4 residues. Taken together, these results suggest that LRMP inhibits HCN4 through an isoform-specific interaction involving the N-terminals of both proteins that prevents the transduction of cAMP binding into a change in channel gating via an HCN4-specific orientation of the N-terminus, C-linker, and S4-S5 linker.
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Affiliation(s)
- Colin H Peters
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
| | - Rohit K Singh
- Skaggs School of Pharmacy, Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, 12850 E. Montview Boulevard, Aurora, CO 80045
| | - Avery A Langley
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
| | - William G Nichols
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
| | - Hannah R Ferris
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
| | - Danielle A Jeffrey
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
- Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, 12631 E. 17 Avenue, Aurora, CO 80045
| | - John R Bankston
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 12800 E. 19 Avenue, Aurora, CO 80045
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Ferris HR, Stine NC, Hill-Eubanks DC, Nelson MT, Wellman GC, Koide M. Epidermal Growth Factor Receptors in Vascular Endothelial Cells Contribute to Functional Hyperemia in the Brain. Int J Mol Sci 2023; 24:16284. [PMID: 38003472 PMCID: PMC10671586 DOI: 10.3390/ijms242216284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/06/2023] [Accepted: 11/12/2023] [Indexed: 11/26/2023] Open
Abstract
Functional hyperemia-activity-dependent increases in local blood perfusion-underlies the on-demand delivery of blood to regions of enhanced neuronal activity, a process that is crucial for brain health. Importantly, functional hyperemia deficits have been linked to multiple dementia risk factors, including aging, chronic hypertension, and cerebral small vessel disease (cSVD). We previously reported crippled functional hyperemia in a mouse model of genetic cSVD that was likely caused by depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) in capillary endothelial cells (EC) downstream of impaired epidermal growth factor receptor (EGFR) signaling. Here, using EC-specific EGFR-knockout (KO) mice, we directly examined the role of endothelial EGFR signaling in functional hyperemia, assessed by measuring increases in cerebral blood flow in response to contralateral whisker stimulation using laser Doppler flowmetry. Molecular characterizations showed that EGFR expression was dramatically decreased in freshly isolated capillaries from EC-EGFR-KO mice, as expected. Notably, whisker stimulation-induced functional hyperemia was significantly impaired in these mice, an effect that was rescued by administration of PIP2, but not by the EGFR ligand, HB-EGF. These data suggest that the deletion of the EGFR specifically in ECs attenuates functional hyperemia, likely via depleting PIP2 and subsequently incapacitating Kir2.1 channel functionality in capillary ECs. Thus, our study underscores the role of endothelial EGFR signaling in functional hyperemia of the brain.
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Affiliation(s)
- Hannah R. Ferris
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - Nathan C. Stine
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - David C. Hill-Eubanks
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA
- Division of Cardiovascular Sciences, University of Manchester, Manchester M13 9PL, UK
| | - George C. Wellman
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - Masayo Koide
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA
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Ferris HR, Hill-Eubanks DC, Nelson MT, Wellman GC, Koide M. Epidermal growth factor receptors in vascular endothelial cells contribute to functional hyperemia in the brain. bioRxiv 2023:2023.09.15.557981. [PMID: 37745396 PMCID: PMC10516026 DOI: 10.1101/2023.09.15.557981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Functional hyperemia - activity-dependent increases in local blood perfusion - underlies the on-demand delivery of blood to regions of enhanced neuronal activity, a process that is crucial for brain health. Importantly, functional hyperemia deficits have been linked to multiple dementia risk factors, including aging, chronic hypertension, and cerebral small vessel disease (cSVD). We previously reported crippled functional hyperemia in a mouse model of genetic cSVD that was likely caused by depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) in capillary endothelial cells (EC) downstream of impaired epidermal growth factor receptor (EGFR) signaling. Here, using EC-specific EGFR-knockout (KO) mice, we directly examined the role of endothelial EGFR signaling in functional hyperemia, assessed by measuring increases in cerebral blood flow in response to contralateral whisker stimulation using laser Doppler flowmetry. Molecular characterizations showed that EGFR expression was dramatically decreased in freshly isolated capillaries from EC-EGFR-KO mice, as expected. Notably, whisker stimulation-induced functional hyperemia was significantly impaired in these mice, an effect that was rescued by exogenous administration of PIP2, but not by the EGFR ligand, HB-EGF. These data suggest that the deletion of the EGFR specifically in ECs depletes PIP2 and attenuates functional hyperemia, underscoring the central role of the endothelial EGFR signaling in cerebral blood flow regulation.
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Affiliation(s)
- Hannah R. Ferris
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
| | - David C. Hill-Eubanks
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT, USA
- Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - George C. Wellman
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
| | - Masayo Koide
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT, USA
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Koide M, Harraz OF, Dabertrand F, Longden TA, Ferris HR, Wellman GC, Hill-Eubanks DC, Greenstein AS, Nelson MT. Differential restoration of functional hyperemia by antihypertensive drug classes in hypertension-related cerebral small vessel disease. J Clin Invest 2021; 131:e149029. [PMID: 34351870 PMCID: PMC8439604 DOI: 10.1172/jci149029] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 07/28/2021] [Indexed: 02/05/2023] Open
Abstract
Dementia resulting from small vessel diseases (SVDs) of the brain is an emerging epidemic for which there is no treatment. Hypertension is the major risk factor for SVDs, but how hypertension damages the brain microcirculation is unclear. Here, we show that chronic hypertension in a mouse model progressively disrupts on-demand delivery of blood to metabolically active areas of the brain (functional hyperemia) through diminished activity of the capillary endothelial cell inward-rectifier potassium channel, Kir2.1. Despite similar efficacy in reducing blood pressure, amlodipine, a voltage-dependent calcium-channel blocker, prevented hypertension-related damage to functional hyperemia whereas losartan, an angiotensin II type 1 receptor blocker, did not. We attribute this drug class effect to losartan-induced aldosterone breakthrough, a phenomenon triggered by pharmacological interruption of the renin-angiotensin pathway leading to elevated plasma aldosterone levels. This hypothesis is supported by the finding that combining losartan with the aldosterone receptor antagonist eplerenone prevented the hypertension-related decline in functional hyperemia. Collectively, these data suggest Kir2.1 as a possible therapeutic target in vascular dementia and indicate that concurrent mineralocorticoid aldosterone receptor blockade may aid in protecting against late-life cognitive decline in hypertensive patients treated with angiotensin II type 1 receptor blockers.
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Affiliation(s)
- Masayo Koide
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA
| | - Osama F. Harraz
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA
| | - Fabrice Dabertrand
- Department of Pharmacology, Larner College of Medicine, and,Department of Anesthesiology and,Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Thomas A. Longden
- Department of Pharmacology, Larner College of Medicine, and,Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | | | - Adam S. Greenstein
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA.,Division of Cardiovascular Sciences, School of Medical Sciences and,Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Group, University of Manchester, Manchester, United Kingdom
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA.,Division of Cardiovascular Sciences, School of Medical Sciences and,Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Group, University of Manchester, Manchester, United Kingdom
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Koide M, Ferris HR, Nelson MT, Wellman GC. Impaired Cerebral Autoregulation After Subarachnoid Hemorrhage: A Quantitative Assessment Using a Mouse Model. Front Physiol 2021; 12:688468. [PMID: 34168571 PMCID: PMC8218876 DOI: 10.3389/fphys.2021.688468] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 04/26/2021] [Indexed: 01/01/2023] Open
Abstract
Subarachnoid hemorrhage (SAH) is a common form of hemorrhagic stroke associated with high rates of mortality and severe disability. SAH patients often develop severe neurological deficits days after ictus, events attributed to a phenomenon referred to as delayed cerebral ischemia (DCI). Recent studies indicate that SAH-induced DCI results from a multitude of cerebral circulatory disturbances including cerebral autoregulation malfunction. Cerebral autoregulation incorporates the influence of blood pressure (BP) on arterial diameter in the homeostatic regulation of cerebral blood flow (CBF), which is necessary for maintaining constant brain perfusion during physiological swings in systemic BP. In this study, we quantitatively examined the impact of SAH on cerebral autoregulation using a mouse endovascular perforation model and a newly developed approach combining absolute and relative CBF measurements. This method enables a direct quantitative comparison of cerebral autoregulation between individual animals (e.g., SAH vs. control or sham-operated mice), which cannot be done solely using relative CBF changes by laser Doppler flowmetry. Here, absolute CBF was measured via injection of fluorescent microspheres at a baseline BP. In separate groups of animals, in vivo laser Doppler flowmetry was used to measure relative CBF changes over a range of BP using phlebotomy and the pressor phenylephrine to lower and raise BP, respectively. Absolute CBF measurements from microspheres were then used to calibrate laser Doppler measurements to calculate the relationship between CBF and BP, i.e., “cerebral autoregulation curves.” Un-operated and sham-operated groups exhibited similar cerebral autoregulatory curves, showing comparable levels of relatively constant CBF over a range of BP from ~80 mmHg to ~130 mmHg. In contrast, SAH animals exhibited a narrower autoregulatory range of BP, which was primarily due to a decrease in the upper limit of BP whereby cerebral autoregulation was maintained. Importantly, SAH animals also exhibited a marked decrease in CBF throughout the entire range of BP. In sum, this study provides evidence of the dramatic reduction in cortical CBF and the diminished range of autoregulation after SAH. Furthermore, this novel methodology should pave the way for future studies examining pathological mechanisms and/or therapeutic strategies targeting impaired cerebral autoregulation, a pathology common to many cardiovascular and cerebrovascular disorders.
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Affiliation(s)
- Masayo Koide
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, United States.,Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine, University of Vermont, Burlington, VT, United States
| | - Hannah R Ferris
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, United States
| | - Mark T Nelson
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, United States.,Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine, University of Vermont, Burlington, VT, United States.,Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - George C Wellman
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, United States
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