Cytoplasmic nucleic acid-based XNAs directly enhance live cardiac cell function by a Ca2+ cycling-independent mechanism via the sarcomere

Abstract

Nucleic acid -protein interactions are critical for regulating gene activation in the nucleus. In the cytoplasm, however, potential nucleic acid-protein functional interactions are less clear. The emergence of a large and expanding number of non-coding RNAs and DNA fragments raises the possibility that the cytoplasmic nucleic acids may interact with cytoplasmic cellular components to directly alter key biological processes within the cell. We now show that both natural and synthetic nucleic acids, collectively XNAs, when introduced to the cytoplasm of live cell cardiac myocytes, markedly enhance contractile function via a mechanism that is independent of new translation, activation of the TLR-9 pathway or by altered intracellular Ca 2+ cycling. Findings show a steep XNA oligo length-dependence, but not sequence dependence or nucleic acid moiety dependence, for cytoplasmic XNAs to hasten myocyte relaxation. XNAs localized to the sarcomere in a striated pattern and bound the cardiac troponin regulatory complex with high affinity in an electrostaticdependent manner. Mechanistically, XNAs phenocopy PKA-based modified troponin to cause faster relaxation. Collectively, these data support a new role for cytoplasmic nucleic acids in directly modulating live cell cardiac performance and raise the possibility that cytoplasmic nucleic acid -protein interactions may alter functionally relevant pathways in other cell types.

Oxidative stress pathogenically remodels the cardiac myocyte cytoskeleton via structural alterations to the microtubule lattice

“…To examine microtubule organization in cardiac myocytes subjected to oxidative stress, rat ventricular cardiac myocytes were isolated and adhered to coverslips placed in 6-well plates, as previously described (Thompson et al, 2019). We then subjected isolated rat cardiac ventricular myocytes to 100-1000 µM hydrogen peroxide (H 2 O 2 ), a reactive oxygen species that is upregulated in ischemic cardiac myocytes (Slezak et al, 1995).…”

“…Adult rat ventricular myocytes were isolated as previously described (Thompson et al, 2016(Thompson et al, , 2019.…”