Hadp1, a newly identified pleckstrin homology domain protein, is required for cardiac contractility in zebrafish

Abstract

SUMMARYThe vertebrate heart is one of the first organs to form, and its early function and morphogenesis are crucial for continued embryonic development. Here we analyze the effects of loss of Heart adaptor protein 1 (Hadp1), which we show is required for normal function and morphogenesis of the embryonic zebrafish heart. Hadp1 is a pleckstrin homology (PH)-domain-containing protein whose expression is enriched in embryonic cardiomyocytes. Knockdown of hadp1 in zebrafish embryos reduced cardiac contractility and altered late myocyte differentiation. By using optical mapping and submaximal levels of hadp1 knockdown, we observed profound effects on Ca2+ handling and on action potential duration in the absence of morphological defects, suggesting that Hadp1 plays a major role in the regulation of intracellular Ca2+ handling in the heart. Hadp1 interacts with phosphatidylinositol 4-phosphate [PI4P; also known as PtdIns(4)P] derivatives via its PH domain, and its subcellular localization is dependent upon this motif. Pharmacological blockade of the synthesis of PI4P derivatives in vivo phenocopied the loss of hadp1 in zebrafish. Collectively, these results demonstrate that hadp1 is required for normal cardiac function and morphogenesis during embryogenesis, and suggest that hadp1 modulates Ca2+ handling in the heart through its interaction with phosphatidylinositols.

ETS Factors Regulate Vegf-Dependent Arterial Specification

“…Histology and in situ hybridization (Dodou et al, 2003; Wythe et al, 2011), ink injections (Krebs et al, 2004) and CD31 immunofluorescence (Coultas et al, 2010) were performed as described elsewhere.…”

“…Cells were starved overnight, and treated with 50 ng/ml recombinant Vegf-A 165 (R&D Systems) for 20 minutes before harvesting for sub-cellular fractionation, as previously described (Wythe et al, 2011). HUVEC and HUAEC lysates were purchased from Sciencell.…”

Mutation of Plekha7 attenuates salt-sensitive hypertension in the rat

“…6 A and B), suggesting that mutation of Plekha7 improves NO bioavailability. Previous studies suggest that NO production is Ca 2+ -dependent (28,29) and that PH domain-containing proteins interact with phosphatidylinositol members to regulate intracellular Ca 2+ signaling (30,31). Because Plekha7 contains a PH domain, we hypothesized that this protein influences NO production by modulating endothelial-specific Ca 2+ signaling.…”

“…Our whole-animal phenotyping suggested that Plekha7 has a vascular role in BP regulation, prompting us to begin to elucidate the downstream pathways that might mediate Plekha7 signaling. Plekha7 is a cell-surface protein with a PH domain that we hypothesize interacts with phospholipids to affect intracellular levels of Ca 2+ (30,31,40), the central mediator of vascular tone (41). Knockdown of HADP1, the closest known orthologous protein to PLEKHA7 in zebrafish, was shown to regulate intracellular Ca 2+ signaling by interaction with the phosphatidylinositol 4-kinase pathway (31).…”

“…Plekha7 is a cell-surface protein with a PH domain that we hypothesize interacts with phospholipids to affect intracellular levels of Ca 2+ (30,31,40), the central mediator of vascular tone (41). Knockdown of HADP1, the closest known orthologous protein to PLEKHA7 in zebrafish, was shown to regulate intracellular Ca 2+ signaling by interaction with the phosphatidylinositol 4-kinase pathway (31). Furthermore, other PLEKHA family members directly interact with phosphoinositide members and influence Ca 2+ release from intracellular stores, suggesting that Plekha7 may be working through similar mechanisms (42,43).…”