Molecular Cardiology

Lab Head:                A/Prof Elizabeth A Woodcock

Phone:                      8532 1255

Email:                        liz.woodcock@bakeridi.edu.au

Dr Peter Iliades                                                         Albert Wong

Dr David Grubb                                                         Tiffany Keef (McLeod-Dryden)

Dr Nicola Cooley                                                       Jieting Luo

Ranjana Liyanage

Available projects for Hons or PhD students

The central role of PLC 1b in atrial pathology

We have shown that PLC 1b is the major PLC subtype in heart and that this PLC is elevated in atria from valvular heart disease patients and in a mouse model with dilated cardiomyopathy.  We have prepared adenoviruses expressing the active PLC and these viruses can be used in studies with isolated cardiomyocytes.  In addition, we have designed and made an inhibitory mini-gene that selectively inhibits PLC 1b activity.  This mini-gene is currently being incorporated into a transgenic mouse line by our collaborators in St Louis. 

The proposed studies will involve the following:

  • Examining signalling responses in these mini gene expressing mice.
  • Crossing these mini-gene mice with the mice with dilated cardiomyopathy to evaluate the contribution of PLC 1b to the disease. 
  • Examining arrhythmogenic responses in the mice to define the involvement of PLC1b to this pathological response.

The relationship between PLC activity and atrial dilatation

Atrial dilatation is a major contributor to cardiac disease, especially atrial fibrillation.  We have shown that there is a correlation between the size of the left atrium of both humans and mice and the activity of PLC.  We now need to show whether increased PLC activity causes dilatation or whether dilatation causes increased PLC activity.  We have also shown that overexpression of PLC 1b in cardiomyocytes causes cell death and death of cardiomyocytes is a major cause of dilatation.

The proposed experiments are as follows:

  • Overexpress PLC 1b in hearts or atria of mice and show that this causes dilatation.
  • A number of different models will be sued that show atrial dilatation and PLC 1b expression and activity will be measured.

How does PLC 1b bind to the cardiomyocyte membrane to be selectively active and cause pathological problems?

We have shown that the unique C-terminal tail of PLC1b is responsible for its binding to the sarcolemma.  However, in order to develop selective drugs to prevent this binding and thus inhibit PLC1b activity in heart, we need to establish exactly how this interaction occurs. 

The studies will involve:

  • Molecular studies to identify amino acid residues involved.  This involves mutagenesis followed by preparation of adenoviruses for use with cardiomyocytes in culture. 
  • Identification of the interacting proteins.  We have identified a possible candidate using yeast-2-hybrid technology, a protein called abLIM-1.  The project will involve using si-RNA technology to lower the expression of abLIM1 to demonstrate its requirement for PLC 1b responses.  We have developed adenoviral vectors for this purpose.  Co-immunoprecipitation and localization studies will also be preformed.

The significance of phospholipase C in atrial dilatation

Phospholipase C (PLC is a newly described PLC subtype that is expressed in heart.  PLC is a very large protein with a MW of 250 kDa comprised of a number of different functional modules.  Currently unpublished data from one of our major collaborators Dr Joan Heller Brown, Department of Pharmacology, UCSD, has shown that PLC mediates responses to thrombin in cardiomyocytes.

Recent studies from our laboratory show that PLC expression is increased in the dilated atria of patients with valvular heart disease and also in a mouse model that has dilated atria.  This suggests a relationship to atrial disease, especially dilatation.  The dilated human and mouse atria contain thrombi and these will provide a local source of thrombin to activate the heightened PLC.  Therefore we think that thrombin/PLC may contribute to atrial pathology directly.

The proposed studies will involve the following:

  • Measuring thrombin activated PLC responses in human atrial tissue from valve patients and controls. 
  • Similar experiments involving atria from the mice with dilated cardiomyopathy.
  • Measuring the changes in PLC expression in relation to the progression of disease in the mouse model. 
  • Assessing the effect of the thrombus, by measuring PLC activity in mouse atria wit and without thrombus. 
  • Crossing the mouse cardiomyopathy model with PLC -/- mice to establish the contribution to disease.