A modular mRNA approach to study and treat phospholamban mediated cardiomyopathies

In the heart, phospholamban (PLN) is a key regulator of calcium cycling through its inhibitory effect on the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump. For more than two decades, modulating calcium channels has been a strong focus of prospective cardiac therapeutics with a recent emphasis on targeting PLN itself, partially due to the progressive uncovering of several cardiomyopathic PLN human mutations. Our understanding of the physiological and pathophysiological mechanisms regulating or misregulating calcium cycling in humans in not fully understood. Therefore, careful study of naturally occurring human mutations can offer important insights into these mechanisms.

This thesis focuses on developing novel investigative and potential therapeutic tools to mechanically dissect and treat phospholamban mediated cardiomyopathies. The constituent papers compiled in this thesis validates these novel and innovative approaches which utilize an mRNA modular system to model and dissect core mechanistic differences caused by cardiomyopathic phospholamban mutations in embryonic stem cell derived cardiomyocytes. Additionally, this thesis showcases the usage of single-chain VHH antibodies (intrabodies) to express, target and modulate PLN intracellularly in vitro and in vivo with promising results validating its usage as a potential therapy and valuable investigative tool.

List of scientific papers

I. Rohner E.; Sahara M.; Chien K.R. The interactive relationship between phospholamban and its pathological mutants. [Manuscript]

II. Rohner E.; Witman N.; Sohlmér J.; De Genst E.; Louch W.E.; Sahara M.; Chien K.R. An mRNA assay system demonstrates proteasomal-specific degradation contributes to cardiomyopathic phospholamban null mutation. Molecular Medicine. 2021, 27, 102.
https://doi.org/10.1186/s10020-021-00362-8

III. De Genst E.; Foo K.S.; Xiao Y.; Rohner E.; De Vries E.; Sohlmér J.; Witman N.; Hidalgo A.; Kolstad T.RS.; Louch W.E.; Pehrsson S.; Park A.; Ikeda Y.; Li X.; Mayr L.M.; Wickson K.; Jennbacken K.; Hansson K.; Fritsche-Danielson R.; Hunt J.; Chien K.R. Blocking phospholamban with VHH intrabodies enhances contractility and relaxation in heart failure. Nature Communications. (2022). [Accepted]
https://doi.org/10.1038/s41467-022-29703-9