Subcellular Ca2+ signalling microdomains regulating cardiomyocyte growth and function

The key research questions in this project are:

• To develop probes for specific modulation and measurement of calcium (Ca2+) concentrations in cellular microdomains.
• To measure Ca2+ changes in cellular microdomains at baseline and in response to cell stimuli that initiate pathological and physiological remodelling of heart muscle cells (hypertrophic growth)
• To test the influence of manipulation of Ca2+ concentrations in cellular microdomains on changes in gene transcription  during the hypertrophic response to physiological and pathological stressors.
• Model interactions between IGF/PI3K  and InsP3 signaling pathways to determine how pathological and physiological hypertrophic stimuli modulate Ca2+ and downstream transcription factor dynamics to induce specific responses.

The graduate researcher on this project is: Joshua Chung

The details

Precise control of intracellular levels of calcium (Ca2+) is essential for heart function. Not only do increases in intracellular Ca2+ induce contraction of heart muscle cells (cardiomyocytes) that are responsible for the pumping of the heart, Ca2+ also participates in the regulation of gene expression that mediates muscle growth (hypertrophy) and modulate metabolism to ensure energy production matches demand.

But it is currently unclear how Ca2+ acts in such a selective manner to precisely control these diverse functions with great fidelity.

Indeed, perturbations of Ca2+ regulatory mechanisms contribute to diminished Ca2+ transients and reduced cardiac contraction, arrhythmias and induction of pathological abnormally thick (hypertrophic) muscle growth that ultimately can lead to heart failure or sudden cardiac death.

We will test the central hypothesis that the partitioning of Ca2+-dependent activities relies upon subcellular Ca2+ signalling microdomains that are coupled to their own specific Ca2+-dependent actions.

Using state-of-the-art nanoscale imaging combined with a genetically-encoded toolkit of Ca2+ signal modulators and reporters to localise Ca2+ handling proteins and membranes we will quantify Ca2+ changes in subcellular microdomains including the nucleus, perinuclear space, dyad and bulk cytosol.

Activation of gene expression will be determined using RNA-Seq, fluorescently-tagged transcription factors and reporters.

Known cues for pathological and physiological hypertrophy as well as strategies for artificially altering intracellular Ca2+ levels will be applied to allow identification of signatures and localisation of Ca2+ signals linked to specific functions.

These data will be used to inform model development, with experiments guided by models generated during the course of this research project.

The project will be complemented by KU Leuven-based project and the collaboration will ensure successful completion of the project.

Supervision team

University of Melbourne participants:

Dr Vijay Rajagopal, Professor Edmund Crampin

KU Leuven participants:

Professor Dr H. Llewelyn Roderick