Altered endoplasmic reticulum calcium loading in human PLN-R14del cardiomyopathy

Area of Science:

• Cardiology
• Molecular Biology
• Cell Biology

Background:

• The phospholamban (PLN) R14del genetic variant is a known cause of dilated cardiomyopathy.
• Previous research suggests the endoplasmic reticulum (ER) stress response and impaired ER-signaling pathways, like autophagy, are involved.
• The precise molecular mechanisms underlying PLN-R14del cardiomyopathy require further elucidation.

Purpose of the Study:

• To investigate the role of ER calcium homeostasis in PLN-R14del cardiomyopathy.
• To validate a novel sensor for measuring ER calcium loading in cardiomyocytes.
• To identify new disease mechanisms associated with the PLN R14del variant.

Main Methods:

• Utilized human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) from control, PLN-R14del patient, and isogenic control cell lines.
• Employed adeno-associated virus serotype 6 (AAV6) to deliver the endoplasmic reticulum calcium sensor CEPIAer.
• Constructed engineered heart tissues (EHTs) and performed Fluorescence-Activated Cell Sorting (FACS) analyses.

Main Results:

• CEPIAer fluorescence intensity effectively served as a surrogate for ER calcium loading across all cell types.
• PLN-R14del cardiomyocytes exhibited subtle alterations in cytoplasmic calcium handling consistent with increased ER calcium loading.
• FACS analysis confirmed a higher ER calcium load in cardiomyocytes from PLN-R14del patients.

Conclusions:

• Altered ER calcium loading represents a newly identified disease mechanism in PLN-R14del cardiomyopathy.
• This finding offers a potential new therapeutic target for managing dilated cardiomyopathy caused by PLN variants.
• The study validates CEPIAer as a reliable tool for assessing ER calcium dynamics in cardiac research.