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

Four-and-a-half LIM-protein 2 (FHL-2), adenylate kinase (AK), and phosphofructokinase 2 (PFK2) levels are significantly decreased in the failing human heart. A, Representative Western blot of FHL2 in patients from the donor, nonfailing, and failing groups. β-Actin was used as a loading control. Each lane represents a different heart. A selection of patients is shown. Densitometric analyses of blots were performed, and the ratio of protein band intensity to β-actin band intensity was used to compare relative amounts of each protein. FHL2 levels were decreased by 53% compared with normal levels (B). AK levels decreased by 48% (C) and PFK2 levels decreased by 57% (E) compared with levels in the control group. CK-M levels decreased slightly (D), but this was not statistically significant. ^∗P < .05.

Four-and-a-half LIM-protein 2 (FHL2) accumulates in discrete cytoplasmic foci in failing human hearts. Representative immunofluorescence microscopic analysis of FHL2 in donor (A), nonfailing (B), and failing (C) left ventricular myocardium. FHL2 (red) in cardiomyocytes from patients with preserved myocardial function (nonfailing group) shows a regular staining pattern indicated by arrowheads and the enlarged section of the merge panel. FHL2 in cardiomyocytes from patients in the failing group is sequestered in discrete cytoplasmic foci (arrows). Phalloidin staining (green) was used to identify cardiomyocytes, and all sections were counterstained with DAPI (blue).

Four-and-a-half LIM-protein 2 (FHL2) colocalizes with the Golgi-specific marker Golgin97 in cardiomyocytes from the failing group. Sections were stained for FHL2 (red) and Golgin97 (green) and counterstained with DAPI. The majority of FHL2 staining is present in the Golgi (arrowheads), but not all Golgi have FHL2 staining (arrows). A 1.0-μm confocal section is shown.

Adenylate kinase (AK), creatine kinase isoform M (CK-M), and phosphofructokinase 2 (PFK2) maintain their interaction with four-and-a-half LIM-protein 2 (FHL2) in the failing heart. Coimmunoprecipitation from extracts of patient hearts from each group shows that AK, CK-M, and PFK2 are in a complex with FHL2. A representative result is shown. Coimmunoprecipitations were performed from every sample. WB, Western blot.

Adenylate kinase (AK), creatine kinase isoform M (CK-M), and phosphofructokinase 2 (PFK2) are also present in the Golgi apparatus in the failing heart. PFK2, AK, and CK-M (A, B, and C, respectively) all colocalize with Golgin97 (green) in the Golgi apparatus of failing cardiomyocytes. Confocal sections of 1.0 μm are shown. A representative result is shown. Staining was performed on every sample.