Reduction of four-and-a-half LIM-protein 2 expression occurs in human left ventricular failure and leads to altered localization and reduced activity of metabolic enzymes.

OBJECTIVE: We sought to identify changes in four-and-a-half LIM-protein 2 levels and location in human cardiomyocytes during the transition from compensated aortic stenosis to left ventricular failure. We also sought to characterize four-and-a-half LIM-protein 2 binding with the metabolic enzymes phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform during this transition and their consequential subcellular localization in failing human ventricles.
METHODS: Left ventricular biopsy specimens from selected patients undergoing aortic valve replacement for aortic stenosis were allocated to one of 2 groups: (1) nondilated with preserved left ventricular function (nonfailing group, n = 16) and (2) grossly dilated with poor left ventricular function (failing group, n = 15). These were compared with a control group of unused donor hearts (n = 6). Protein levels and subcellular localization were determined by means of Western blotting and immunofluorescence. Four-and-a-half LIM-protein 2 binding to adenylate kinase, creatine kinase M isoform, or phosphofructokinase 2 was studied by means of coimmunoprecipitation. Phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform activities were assayed in protein extractions.
RESULTS: Four-and-a-half LIM-protein 2 levels were preserved in nonfailing hypertrophied hearts but reduced by 53% in failing hearts. The pattern of four-and-a-half LIM-protein 2 staining was disrupted in failing hearts: four-and-a-half LIM-protein 2 was lost from the sarcomere but present in the perinuclear Golgi apparatus complex. Phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform coimmunoprecipitated in vitro and colocalized with four-and-a-half LIM-protein 2 in both hypertrophied and failing hearts. Phosphofructokinase 2 and adenylate kinase activities were reduced to 77% and 58% of normal values in compensated aortic stenosis, with phosphofructokinase 2 activity decreased further to 56% of normal value in failing hearts, but creatine kinase activity remained unchanged.
CONCLUSIONS: Altered four-and-a-half LIM-protein 2 expression in heart failure is associated with disruption of the normal subcellular localization of phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform and reduced activity of phosphofructokinase 2 and adenylate kinase, which might have important consequences for myocardial energy metabolism in heart failure.