Polycystin-1 Is a Crucial Regulator of BIN1 Expression and T-Tubule Remodeling Associated with the Development of Dilated Cardiomyopathy

Abstract

Cardiomyopathy is commonly observed in patients with autosomal dominant polycystic kidney disease (ADPKD), even when they have normal renal function and arterial pressure. The role of cardiomyocyte polycystin-1 (PC1) in cardiovascular pathophysiology remains unknown. PC1 is a potential regulator of BIN1 that maintains T-tubule structure, and alterations in BIN1 expression induce cardiac pathologies. We used a cardiomyocyte-specific PC1-silenced (PC1-KO) mouse model to explore the relevance of cardiomyocyte PC1 in the development of heart failure (HF), considering reduced BIN1 expression induced T-tubule remodeling as a potential mechanism. PC1-KO mice exhibited an impairment of cardiac function, as measured by echocardiography, but no signs of HF until 7-9 months of age. Of the PC1-KO mice, 43% died suddenly at 7 months of age, and 100% died after 9 months with dilated cardiomyopathy. Total BIN1 mRNA, protein levels, and its localization in plasma membrane-enriched fractions decreased in PC1-KO mice. Moreover, the BIN1 + 13 isoform decreased while the BIN1 + 13 + 17 isoform was overexpressed in mice without signs of HF. However, BIN1 + 13 + 17 overexpression was not observed in mice with HF. T-tubule remodeling and BIN1 score measured in plasma samples were associated with decreased PC1-BIN1 expression and HF development. Our results show that decreased PC1 expression in cardiomyocytes induces dilated cardiomyopathy associated with diminished BIN1 expression and T-tubule remodeling. In conclusion, positive modulation of BIN1 expression by PC1 suggests a novel pathway that may be relevant to understanding the pathophysiological mechanisms leading to cardiomyopathy in ADPKD patients.

Keywords: BIN1; T-tubule; dilated cardiomyopathy; heart failure; polycystin-1.

Figure 1

Dilated cardiomyopathy associated with loss of polycystin-1 expression. (A) Kaplan–Meier curves showing survival of PC1-KO mice (n = 12–14). (B) Ejection fraction (EF) and (C) Fractional shortening (FS) of PC1^F/F and PC1-KO mice without (<7 months old, n = 5–7) and with (7–9 months old, n = 5–8) signs of HF. (D) Four-chamber-view hematoxylin/eosin staining (Scale bar: 300 μm). (E) Heart weight/tibia length (HW/TL) in animals without (n = 7–10) or with (n = 12–13) signs of HF. (F) Lung wet weight/tibia length (LWW/TL, n = 11–13). Values shown are the means ± SEM and were analyzed using the Student t test. * p < 0.05; ** p < 0.005; *** p < 0.001 vs. PC1^F/F.

Figure 2

Bin1 expression and localization in cardiac tissue of PC1-KO mice. Representative Western blots and BIN1 protein quantification in samples from <7 months old (A, n = 6) and 7–9-month-old (B, n = 4–5) PC1^F/F and PC1-KO mice. Total BIN1 mRNA content at <7 months old (C, n = 7–8) and 7–9 months old (D, n = 8–11) in samples from PC1^F/F and PC1-KO mice. (E,F) Representative Western blots and quantification of BIN1 in plasma membrane-enriched fractions (n = 3). H: homogenate; MS: microsomes enriched in surface membrane; C: cytosolic fraction. Values shown are the means ±SEM and were analyzed using the Student t test. * p < 0.05 vs. PC1^F/F.

Figure 3

Cardiac BIN1 isoform expression is regulated by polycystin-1. BIN1 + 13 mRNA quantification in PC1^F/F and PC1-KO cardiac tissue samples from <7 months old (A, n = 9) and 7–9-month-old (B, n = 6–7) mice. BIN1 + 13 + 17 mRNA levels in PC1^F/F and PC1-KO cardiac tissue from <7 months old (C, n = 9) and 7–9-month-old (D, n = 6–7) mice. Values shown are the means ± SEM and were analyzed using the Student t test. * p < 0.05; ** p < 0.005 vs. PC1^F/F.

Figure 4

Correlation between polycystin-1 expression in cardiomyocytes and T-tubule remodeling. (A) Representative transmission electron microscope images of T-tubules from PC1^F/F and PC1-KO cardiac tissue of <7-month- and 7–9-month-old mice. In addition, the quantification of lumen area (B,D) and the lumen electron density (C,E) of T-tubules is shown. Scale bars 500 nm. (F,G) Lumen electron density of PC1-KO mice <7 months and 7–9 months of age. T-tubules were measured for 3–4 mice per genotype. Roughly 8–10 ventricular sections and 103–124 and 211–235 T-tubules were evaluated per condition in mice <7 months and 7–9 months of age, respectively. (H,I) Ratio of T-tubules number/area for cardiac tissue from PC1^F/F and PC1-KO mice. Values shown are the means ± SEM, and were analyzed by the Student t test. * p < 0.05; *** p < 0.001 vs. PC1^F/F.

Figure 4

Correlation between polycystin-1 expression in cardiomyocytes and T-tubule remodeling. (A) Representative transmission electron microscope images of T-tubules from PC1^F/F and PC1-KO cardiac tissue of <7-month- and 7–9-month-old mice. In addition, the quantification of lumen area (B,D) and the lumen electron density (C,E) of T-tubules is shown. Scale bars 500 nm. (F,G) Lumen electron density of PC1-KO mice <7 months and 7–9 months of age. T-tubules were measured for 3–4 mice per genotype. Roughly 8–10 ventricular sections and 103–124 and 211–235 T-tubules were evaluated per condition in mice <7 months and 7–9 months of age, respectively. (H,I) Ratio of T-tubules number/area for cardiac tissue from PC1^F/F and PC1-KO mice. Values shown are the means ± SEM, and were analyzed by the Student t test. * p < 0.05; *** p < 0.001 vs. PC1^F/F.

Figure 5

Changes in the BIN1 score of PC1-KO mice correlated with cardiac dysfunction. Bar graph of the BIN1 score obtained evaluating PC1^F/F and PC1-KO mice at <7 months (A, n = 4 per duplicated) and 7–9 months of age (B, n= 5–6, per duplicated). Values shown are the means ± SEM and were analyzed using the Student t test. * p < 0.05 vs. PC1^F/F.

Figure 6

Graphical model depicting how polycystin-1-dependent BIN1 expression relates to T-tubule remodeling and cardiac dysfunction. (A) Normal cardiac function: PC1 positively regulates BIN1 expression and therefore T-tubule formation with microfolds. cBIN (BIN1 + 13 + 17 isoform) is released in vesicles to the extracellular space. (B) Decreased cardiac function without signs of HF: Total BIN1 expression and BIN1 + 13 isoform decrease in cardiospecific PC1-KO mice (<7 months) while BIN1 + 13 + 17 isoform increase leading to the loss of T-tubule microfolds and to an increase in plasma cBIN1, and; (C) Heart failure and development of dilated cardiomyopathy: Total BIN1, BIN1 + 13 and BIN1 + 13 + 17 expression decrease in cardiomyocytes from PC1-KO mice (7–9-month), exacerbating the loss of T-tubules and microfolds and decreasing the release of cBIN1 to the plasma. The figure was created with BioRender.com (accessed on 29 December 2021).