Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling
Mutations in thin filament regulatory proteins that cause hypertrophic cardiomyopathy (HCM) increase myofilament Ca2+ sensitivity. Mouse models exhibit increased Ca2+ buffering and arrhythmias, and we hypothesized that these changes are primary effects of the mutations (independent of compensatory c...
| Glavni autori: | , , , , , , , |
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| Format: | Journal article |
| Jezik: | English |
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American Society for Biochemistry and Molecular Biology
2018
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| _version_ | 1826300458755424256 |
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| author | Robinson, P Liu, X Sparrow, A Patel, S Zhang, Y Casadei, B Watkins, H Redwood, C |
| author_facet | Robinson, P Liu, X Sparrow, A Patel, S Zhang, Y Casadei, B Watkins, H Redwood, C |
| author_sort | Robinson, P |
| collection | OXFORD |
| description | Mutations in thin filament regulatory proteins that cause hypertrophic cardiomyopathy (HCM) increase myofilament Ca2+ sensitivity. Mouse models exhibit increased Ca2+ buffering and arrhythmias, and we hypothesized that these changes are primary effects of the mutations (independent of compensatory changes) and that increased Ca2+ buffering and altered Ca2+ handling contribute to HCM pathogenesis via activation of Ca2+-dependent signaling. Here, we determined the primary effects of HCM mutations on intracellular Ca2+ handling and Ca2+-dependent signaling in a model system possessing Ca2+-handling mechanisms and contractile protein isoforms closely mirroring the human environment in the absence of potentially confounding remodeling. Using adenovirus, we expressed HCM-causing variants of human troponin-T, troponin-I, and α-tropomyosin (R92Q, R145G, and D175N, respectively) in isolated guinea pig left ventricular cardiomyocytes. After 48 h, each variant had localized to the I-band and comprised ∼50% of the total protein. HCM mutations significantly lowered the Kd of Ca2+ binding, resulting in higher Ca2+ buffering of mutant cardiomyocytes. We observed increased diastolic [Ca2+] and slowed Ca2+ reuptake, coupled with a significant decrease in basal sarcomere length and slowed relaxation. HCM mutant cells had higher sodium/calcium exchanger activity, sarcoplasmic reticulum Ca2+ load, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) activity driven by Ca2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylation of phospholamban. The ryanodine receptor (RyR) leak/load relationship was also increased, driven by CaMKII-mediated RyR phosphorylation. Altered Ca2+ homeostasis also increased signaling via both calcineurin/NFAT and extracellular signal–regulated kinase pathways. Altered myofilament Ca2+ buffering is the primary initiator of signaling cascades, indicating that directly targeting myofilament Ca2+ sensitivity provides an attractive therapeutic approach in HCM. |
| first_indexed | 2024-03-07T05:17:29Z |
| format | Journal article |
| id | oxford-uuid:ddb46300-bc2e-4f95-a488-aadc88dae47e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:17:29Z |
| publishDate | 2018 |
| publisher | American Society for Biochemistry and Molecular Biology |
| record_format | dspace |
| spelling | oxford-uuid:ddb46300-bc2e-4f95-a488-aadc88dae47e2022-03-27T09:27:01ZHypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signalingJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:ddb46300-bc2e-4f95-a488-aadc88dae47eEnglishSymplectic Elements at OxfordAmerican Society for Biochemistry and Molecular Biology2018Robinson, PLiu, XSparrow, APatel, SZhang, YCasadei, BWatkins, HRedwood, CMutations in thin filament regulatory proteins that cause hypertrophic cardiomyopathy (HCM) increase myofilament Ca2+ sensitivity. Mouse models exhibit increased Ca2+ buffering and arrhythmias, and we hypothesized that these changes are primary effects of the mutations (independent of compensatory changes) and that increased Ca2+ buffering and altered Ca2+ handling contribute to HCM pathogenesis via activation of Ca2+-dependent signaling. Here, we determined the primary effects of HCM mutations on intracellular Ca2+ handling and Ca2+-dependent signaling in a model system possessing Ca2+-handling mechanisms and contractile protein isoforms closely mirroring the human environment in the absence of potentially confounding remodeling. Using adenovirus, we expressed HCM-causing variants of human troponin-T, troponin-I, and α-tropomyosin (R92Q, R145G, and D175N, respectively) in isolated guinea pig left ventricular cardiomyocytes. After 48 h, each variant had localized to the I-band and comprised ∼50% of the total protein. HCM mutations significantly lowered the Kd of Ca2+ binding, resulting in higher Ca2+ buffering of mutant cardiomyocytes. We observed increased diastolic [Ca2+] and slowed Ca2+ reuptake, coupled with a significant decrease in basal sarcomere length and slowed relaxation. HCM mutant cells had higher sodium/calcium exchanger activity, sarcoplasmic reticulum Ca2+ load, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) activity driven by Ca2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylation of phospholamban. The ryanodine receptor (RyR) leak/load relationship was also increased, driven by CaMKII-mediated RyR phosphorylation. Altered Ca2+ homeostasis also increased signaling via both calcineurin/NFAT and extracellular signal–regulated kinase pathways. Altered myofilament Ca2+ buffering is the primary initiator of signaling cascades, indicating that directly targeting myofilament Ca2+ sensitivity provides an attractive therapeutic approach in HCM. |
| spellingShingle | Robinson, P Liu, X Sparrow, A Patel, S Zhang, Y Casadei, B Watkins, H Redwood, C Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling |
| title | Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling |
| title_full | Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling |
| title_fullStr | Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling |
| title_full_unstemmed | Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling |
| title_short | Hypertrophic cardiomyopathy mutations increase myofilament Ca2+ buffering, alter intracellular Ca2+ handling, and stimulate Ca2+-dependent signaling |
| title_sort | hypertrophic cardiomyopathy mutations increase myofilament ca2 buffering alter intracellular ca2 handling and stimulate ca2 dependent signaling |
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