Ca2+/calmodulin‐dependent protein kinase II and protein kinase G oxidation contributes to impaired sarcomeric proteins in hypertrophy model

Abstract

Aims Volume overload (VO) induced hypertrophy is one of the hallmarks to the development of heart diseases. Understanding the compensatory mechanisms involved in this process might help preventing the disease progression. Methods and resultsTherefore, the present study used 2 months old Wistar rats, which underwent an aortocaval fistula to develop VO-induced hypertrophy. The animals were subdivided into four different groups, two sham operated animals served as age-matched controls and two groups with aortocaval fistula. Echocardiography was performed prior termination after 4and 8-month. Functional and molecular changes of several sarcomeric proteins and their signalling pathways involved in the regulation and modulation of cardiomyocyte function were investigated. ResultsThe model was characterized with preserved ejection fraction in all groups and with elevated heart/body weight ratio, left/right ventricular and atrial weight at 4-and 8-month, which indicates VO-induced hypertrophy. In addition, 8-months groups showed increased left ventricular internal diameter during diastole, RV internal diameter, stroke volume and velocity-time index compared with their age-matched controls. These changes were accompanied by increased Ca 2+ sensitivity and titin-based cardiomyocyte stiffness in 8-month VO rats compared with other groups. The altered cardiomyocyte mechanics was associated with phosphorylation deficit of sarcomeric proteins cardiac troponin I, myosin binding protein C and titin, also accompanied with impaired signalling pathways involved in phosphorylation of these sarcomeric proteins in 8-month VO rats compared with age-matched control group. Impaired protein phosphorylation status and dysregulated signalling pathways were associated with significant alterations in the oxidative status of both kinases CaMKII and PKG explaining by this the elevated Ca 2+ sensitivity and titin-based cardiomyocyte stiffness and perhaps the development of hypertrophy. Conclusions Our findings showed VO-induced cardiomyocyte dysfunction via deranged phosphorylation of myofilament proteins and signalling pathways due to increased oxidative state of CaMKII and PKG and this might contribute to the development of hypertrophy.

CaMKII regulates the proteins TPM1 and MYOM2 and promotes diacetylmorphine-induced abnormal cardiac rhythms

“…MYOM2, a member of the myomesin protein family, is a major component of the myofibrillar myogenic fiber M-band and a central gene in myofibrillar gene interactions 28 . In contrast, CaMKII is a signaling molecule whose activity is triggered by an increase in intracellular Ca 2+ levels, an activity that can be sustained by enzymatic autophosphorylation, generating molecular memory concentrations after a decrease in Ca 2+ ; it regulates a variety of proteins that are involved not only in ECC and relaxation but also in cell death, transcriptional activation of hypertrophy, inflammation, and arrhythmias 29 , 30 . We verified by Western Bloting assay and found that diacetylmorphine increased the phosphorylation level of CaMKII T287 site in cardiomyocytes and increased the relative expression of TPM1 and MYOM2 proteins compared with the con group, while after using CaMKII inhibitor KN-93, compared with the drug group, the phosphorylation level of CaMKII T287 site The relative expression of TPM1 and MYOM2 proteins was decreased.…”

The role of endosarcomeric cytoskeleton proteins in the mechanisms of left ventricular diastolic dysfunction: focus on titin

“…Нарушение фосфорилирования отдельных частей молекулы титина или активацию под влиянием некоторых факторов (например, шаперона Hsp90, индукторов и продуктов окислительного стресса или провоспалительных цитокинов) ее дефосфорилирования серин/треонин фосфатазой 5 относят к титин-зависимым механизмам развития повышения жесткости миокарда и диастолической сердечной недостаточности [12,49,53,54,[95][96][97][98]. Поскольку дифференцированные сегменты отдельных изоформ титина в растяжимой части I-полосы могут фосфорилироваться различными протеинкиназами, что приводит к неодинаковым эффектам, выяснение статуса фосфорилирования титина важно, когда требуется всестороннее понимание механизмов изменения жесткости миокарда при развитии сердечной недостаточности с сохраненной ФВ ЛЖ [80,99].…”