A junctional cAMP compartment regulates rapid Ca2+ signaling in atrial myocytes

Year: 2022

Authors: Brandenburg S., Pawlowitz J., Steckmeister V., Subramanian H., Uhlenkamp D., Scardigli M., Mushtaq M., Amlaz S.I., Kohl T., Wegener J.W., Arvanitis D.A., Sanoudou D., Sacconi L., Hasenfuss G., Voigt N., Nikolaev V.O., Lehnart S.E.

Autors Affiliation: Univ Med Ctr Gottingen, Heart Res Ctr Gottingen, Dept Cardiol & Pneumol, Cellular Biophys & Translat Cardiol Sect, Gottingen, Germany; DZHK German Ctr Cardiovasc Res, Partner Site, Gottingen, Germany; Univ Gottingen, Cluster Excellence Multiscale Bioimaging Mol Machi, Gottingen, Germany; Univ Med Ctr Gottingen, Inst Pharmacol & Toxicol, Heart Res Ctr Gottingen, Gottingen, Germany; Univ Med Ctr Hamburg Eppendorf, Inst Expt Cardiovasc Res, Hamburg, Germany; Univ Florence, Dept Phys & Astro n, Florence, Italy; European Lab Nonlinear Spect, Sesto Fiorentino, Italy; Acad Athens, Biomed Res Fdn, Mol Biol Div, Athens, Greece; Univ Freiburg, Univ Heart Ctr Freiburg, Inst Expt Cardiovasc Med, Fac Med, Freiburg, Germany; DZHK German Ctr Cardiovasc Res, Partner Site, Lubeck, Germany; Natl Inst Opt INO CNR, Sch Med, Ctr Biomed Engn & Technol, BioMET, Sesto Fiorentino, MD, Italy; Univ Med Ctr Gottingen, Robert Koch Str 42a, D-37075 Gottingen, Germany.

Abstract: Axial tubule junctions with the sarcoplasmic reticulum control the rapid intracellular Ca2+-induced Ca2+ release that initiates atrial contraction. In atrial myocytes we previously identified a constitutively increased ryanodine receptor (RyR2) phosphorylation at junctional Ca2+ release sites, whereas non-junctional RyR2 clusters were phosphorylated acutely following beta-adrenergic stimulation. Here, we hypothesized that the baseline synthesis of 3?,5?-cyclic adenosine monophosphate (cAMP) is constitutively augmented in the axial tubule junctional compartments of atrial myocytes. Confocal immunofluorescence imaging of atrial myocytes revealed that junctin, binding to RyR2 in the sarcoplasmic reticulum, was densely clustered at axial tubule junctions. Interestingly, a new transgenic junctin-targeted FRET cAMP biosensor was exclusively co-clustered in the junctional compart-ment, and hence allowed to monitor cAMP selectively in the vicinity of junctional RyR2 channels. To dissect local cAMP levels at axial tubule junctions versus subsurface Ca2+ release sites, we developed a confocal FRET imaging technique for living atrial myocytes. A constitutively high adenylyl cyclase activity sustained increased local cAMP levels at axial tubule junctions, whereas beta-adrenergic stimulation overcame this cAMP compartmentation resulting in additional phosphorylation of non-junctional RyR2 clusters. Adenylyl cyclase inhibition, however, abolished the junctional RyR2 phosphorylation and decreased L-type Ca2+ channel currents, while FRET imaging showed a rapid cAMP decrease. In conclusion, FRET biosensor imaging identified compartmentalized, consti-tutively augmented cAMP levels in junctional dyads, driving both the locally increased phosphorylation of RyR2 clusters and larger L-type Ca2+ current density in atrial myocytes. This cell-specific cAMP nanodomain is maintained by a constitutively increased adenylyl cyclase activity, contributing to the rapid junctional Ca2+- induced Ca2+ release, whereas beta-adrenergic stimulation overcomes the junctional cAMP compartmentation through cell-wide activation of non-junctional RyR2 clusters.

Journal/Review: JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY

Volume: 165      Pages from: 141  to: 157

More Information: This work was supported by Deutsche Forschungsgemeinschaft to SB (SFB1002 project A09), SEL (SFB1002 projects A09 and S02; SFB1190 project P03), GH (SFB1002 project D01), NV (SFB1002 project A13, VO 1568/3-1, VO 1568/4-1, IRTG1816), VON (SFB1002 project A01); and under Germany´s Excellence Strategy -EXC 2067/1-390729940. VON was supported by the Gertraud und Heinz Rose-Foundation. NV received funding from the Else-Kr oner-Fresenius Foundation (EKFS 2016_A20). JP was supported by the German Cardiac Society (Otto-Hess-Scholarship). SB received financial support through a DZHK (German Centre for Cardiovascular Research) postdoc start-up grant (81X3300108), and the clinician scientist program “Translational Medicine” of the University Medical Center Gottingen. GH, NV, SEL, VON are principal investigators of the DZHK (German Centre for Cardiovascular Research).
KeyWords: Adenylyl cyclase; Atrial myocyte; cAMP; Ca2+ signaling; FRET biosensor; Ryanodine receptor
DOI: 10.1016/j.yjmcc.2022.01.003

Citations: 7
data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-11-17
References taken from IsiWeb of Knowledge: (subscribers only)
Connecting to view paper tab on IsiWeb: Click here
Connecting to view citations from IsiWeb: Click here