Abstract
The predominant cardiac Ca 2+/calmodulin-dependent protein kinase (CaMK) is CaMKIIδ. Here we acutely overexpress CaMKIIδ C using adenovirus-mediated gene transfer in adult rabbit ventricular myocytes. This circumvents confounding adaptive effects in CaMKIIδ C transgenic mice. CaMKIIδ C protein expression and activation state (autophosphorylation) were increased 5- to 6-fold. Basal twitch contraction amplitude and kinetics (1 Hz) were not changed in CaMKIIδ C versus LacZ expressing myocytes. However, the contraction-frequency relationship was more negative, frequency-dependent acceleration of relaxation was enhanced (τ 0.5Hz/τ 3Hz=2.14±0.10 versus 1.87±0.10), and peak Ca 2+ current (I Ca) was increased by 31% (-7.1±0.5 versus -5.4±0.5 pA/pF, P<0.05). Ca 2+ transient amplitude was not significantly reduced (-27%, P=0.22), despite dramatically reduced sarcoplasmic reticulum (SR) Ca 2+ content (41%; P<0.05). Thus fractional SR Ca 2+ release was increased by 60% (P<0.05). Diastolic SR Ca 2+ leak assessed by Ca 2+ spark frequency (normalized to SR Ca 2+ load) was increased by 88% in CaMKIIδ C versus LacZ myocytes (P<0.05; in an multiplicity-of-infection-dependent manner), an effect blocked by CaMKII inhibitors KN-93 and autocamtide-2-related inhibitory peptide. This enhanced SR Ca 2+ leak may explain reduced SR Ca 2+ content, despite measured levels of SR Ca 2+-ATPaSe and Na +/Ca 2+ exchange expression and function being unaltered. Ryanodine receptor (RyR) phosphorylation in CaMKIIδ C myocytes was increased at both Ser2809 and Ser2815, but FKBP12.6 coimmunoprecipitation with RyR was unaltered. This shows for the first time that acute CaMKIIδ C overexpression alters RyR function, leading to enhanced R Ca 2+ leak and reduced SR Ca 2+ content but without reducing twitch contraction and Ca 2+ transients. We conclude that this is attributable to concomitant enhancement of fractional SR Ca 2+ release in CaMKIIδ C myocytes (ie, CaMKII-dependent enhancement of RyR Ca 2+ sensitivity during diastole and systole) and increased I Ca.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 235-244 |
| Number of pages | 10 |
| Journal | Circulation Research |
| Volume | 98 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 2006 |
| Externally published | Yes |
Fingerprint
Keywords
- Calcium
- CaMKII
- Excitation-contraction coupling
- Sarcoplasmic reticulum
ASJC Scopus subject areas
- Physiology
- Cardiology and Cardiovascular Medicine
Cite this
Increased sarcoplasmic reticulum calcium leak but unaltered contractility by acute CaMKII overexpression in isolated rabbit cardiac myocytes. / Kohlhaas, Michael; Zhang, Tong; Seidler, Tim; Zibrova, Darya; Dybkova, Nataliya; Steen, Astrid; Wagner, Stefan; Chen, Lu; Brown, Joan Heller; Bers, Donald M; Maier, Lars S.
In: Circulation Research, Vol. 98, No. 2, 02.2006, p. 235-244.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Increased sarcoplasmic reticulum calcium leak but unaltered contractility by acute CaMKII overexpression in isolated rabbit cardiac myocytes
AU - Kohlhaas, Michael
AU - Zhang, Tong
AU - Seidler, Tim
AU - Zibrova, Darya
AU - Dybkova, Nataliya
AU - Steen, Astrid
AU - Wagner, Stefan
AU - Chen, Lu
AU - Brown, Joan Heller
AU - Bers, Donald M
AU - Maier, Lars S.
PY - 2006/2
Y1 - 2006/2
N2 - The predominant cardiac Ca 2+/calmodulin-dependent protein kinase (CaMK) is CaMKIIδ. Here we acutely overexpress CaMKIIδ C using adenovirus-mediated gene transfer in adult rabbit ventricular myocytes. This circumvents confounding adaptive effects in CaMKIIδ C transgenic mice. CaMKIIδ C protein expression and activation state (autophosphorylation) were increased 5- to 6-fold. Basal twitch contraction amplitude and kinetics (1 Hz) were not changed in CaMKIIδ C versus LacZ expressing myocytes. However, the contraction-frequency relationship was more negative, frequency-dependent acceleration of relaxation was enhanced (τ 0.5Hz/τ 3Hz=2.14±0.10 versus 1.87±0.10), and peak Ca 2+ current (I Ca) was increased by 31% (-7.1±0.5 versus -5.4±0.5 pA/pF, P<0.05). Ca 2+ transient amplitude was not significantly reduced (-27%, P=0.22), despite dramatically reduced sarcoplasmic reticulum (SR) Ca 2+ content (41%; P<0.05). Thus fractional SR Ca 2+ release was increased by 60% (P<0.05). Diastolic SR Ca 2+ leak assessed by Ca 2+ spark frequency (normalized to SR Ca 2+ load) was increased by 88% in CaMKIIδ C versus LacZ myocytes (P<0.05; in an multiplicity-of-infection-dependent manner), an effect blocked by CaMKII inhibitors KN-93 and autocamtide-2-related inhibitory peptide. This enhanced SR Ca 2+ leak may explain reduced SR Ca 2+ content, despite measured levels of SR Ca 2+-ATPaSe and Na +/Ca 2+ exchange expression and function being unaltered. Ryanodine receptor (RyR) phosphorylation in CaMKIIδ C myocytes was increased at both Ser2809 and Ser2815, but FKBP12.6 coimmunoprecipitation with RyR was unaltered. This shows for the first time that acute CaMKIIδ C overexpression alters RyR function, leading to enhanced R Ca 2+ leak and reduced SR Ca 2+ content but without reducing twitch contraction and Ca 2+ transients. We conclude that this is attributable to concomitant enhancement of fractional SR Ca 2+ release in CaMKIIδ C myocytes (ie, CaMKII-dependent enhancement of RyR Ca 2+ sensitivity during diastole and systole) and increased I Ca.
AB - The predominant cardiac Ca 2+/calmodulin-dependent protein kinase (CaMK) is CaMKIIδ. Here we acutely overexpress CaMKIIδ C using adenovirus-mediated gene transfer in adult rabbit ventricular myocytes. This circumvents confounding adaptive effects in CaMKIIδ C transgenic mice. CaMKIIδ C protein expression and activation state (autophosphorylation) were increased 5- to 6-fold. Basal twitch contraction amplitude and kinetics (1 Hz) were not changed in CaMKIIδ C versus LacZ expressing myocytes. However, the contraction-frequency relationship was more negative, frequency-dependent acceleration of relaxation was enhanced (τ 0.5Hz/τ 3Hz=2.14±0.10 versus 1.87±0.10), and peak Ca 2+ current (I Ca) was increased by 31% (-7.1±0.5 versus -5.4±0.5 pA/pF, P<0.05). Ca 2+ transient amplitude was not significantly reduced (-27%, P=0.22), despite dramatically reduced sarcoplasmic reticulum (SR) Ca 2+ content (41%; P<0.05). Thus fractional SR Ca 2+ release was increased by 60% (P<0.05). Diastolic SR Ca 2+ leak assessed by Ca 2+ spark frequency (normalized to SR Ca 2+ load) was increased by 88% in CaMKIIδ C versus LacZ myocytes (P<0.05; in an multiplicity-of-infection-dependent manner), an effect blocked by CaMKII inhibitors KN-93 and autocamtide-2-related inhibitory peptide. This enhanced SR Ca 2+ leak may explain reduced SR Ca 2+ content, despite measured levels of SR Ca 2+-ATPaSe and Na +/Ca 2+ exchange expression and function being unaltered. Ryanodine receptor (RyR) phosphorylation in CaMKIIδ C myocytes was increased at both Ser2809 and Ser2815, but FKBP12.6 coimmunoprecipitation with RyR was unaltered. This shows for the first time that acute CaMKIIδ C overexpression alters RyR function, leading to enhanced R Ca 2+ leak and reduced SR Ca 2+ content but without reducing twitch contraction and Ca 2+ transients. We conclude that this is attributable to concomitant enhancement of fractional SR Ca 2+ release in CaMKIIδ C myocytes (ie, CaMKII-dependent enhancement of RyR Ca 2+ sensitivity during diastole and systole) and increased I Ca.
KW - Calcium
KW - CaMKII
KW - Excitation-contraction coupling
KW - Sarcoplasmic reticulum
UR - http://www.scopus.com/inward/record.url?scp=33644865926&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33644865926&partnerID=8YFLogxK
U2 - 10.1161/01.RES.0000200739.90811.9f
DO - 10.1161/01.RES.0000200739.90811.9f
M3 - Article
C2 - 16373600
AN - SCOPUS:33644865926
VL - 98
SP - 235
EP - 244
JO - Circulation Research
JF - Circulation Research
SN - 0009-7330
IS - 2
ER -