Increasing prevalence of ischemic heart disease and particularly myocardial infarction (MI) carries a high socioeconomic burden, and treatment strategies are limited. Emerging data from our group have indicated that reduced cardiac contractility in this condition is linked to degradation of subcellular structures called t-tubules. While the underlying mechanisms are unclear, our data suggest that the interplay between the scaffolding protein BIN1 and specific lipids called phospho-inositides (PIs) is critically involved.

The objective of this study is to establish that BIN1 and PI homeostasis precisely controls cardiac t-tubule growth, maturation, and maintenance. We additionally aim to target these pathways to reverse t-tubule remodeling during MI.

We are making use of the HL-1 cardiomyocyte cell line, isolated mouse cardiomyocytes, and an in vivo mouse model of MI to thoroughly study the collaborative roles of BIN1 and PIs in controlling cardiac t-tubule growth. Transcript and protein levels of target proteins in heart tissue are assessed by RT-qPCR and Western-blotting. T-tubule organization is studied by immunofluorescence and immunohistochemistry followed by confocal microscopy.

In a first part, we are working on the establishment of a cardiac “t-tubule interactome” in HL-1 cardiomyocytes, using affinity purification coupled to mass spectrometry to identify key pathways implicated in tubulogenesis and lipid homeostasis. Our initial confirmation by co-localization and Western-blotting, indicates that the BIN1-partners DNM2, MTM1, RIN2, RIN3, and SYNJ2 are the most propitious. We have also started to determine the lipid composition of t-tubules, using probes for membrane polarity and lipidomic.

We are further investigating the promising target proteins in a cardiac disease setting. This work is carried out in a well-established mouse model of acute MI followed by 3h–28days of reperfusion. Our encouraging initial results suggest a downregulation of BIN1 and MTM1 as well as an upregulation of RIN3 at the protein level during MI.

Thus, this work will provide exciting new insight into both the pathophysiology and treatment of MI.