Heterozygous Null Bone Morphogenetic Protein Receptor Type 2 Mutations Promote Src-Dependent Caveolar Trafficking Defects and Endothelial Dysfunction in Pulmonary Arterial Hypertension [Cell Biology]

November 19th, 2014 by Prewitt, A. R., Ghose, S., Frump, A. L., Datta, A., Austin, E. D., Kenworthy, A. K., de Caestecker, M. P.

HPAH is a rare, fatal disease of the pulmonary vasculature. The majority of HPAH patients inherit mutations in the BMP type 2-receptor gene, BMPR2, but how these promote pulmonary vascular disease is unclear. HPAH patients have features of pulmonary endothelial cell (PEC) dysfunction including increased vascular permeability and perivascular inflammation associated with decreased PEC barrier function. Recently, frame-shift mutations in the caveolar structural protein gene, Caveolin 1 (Cav-1), were identified in two patients with non-BMPR2-associated HPAH. Since caveolae regulate endothelial function and vascular permeability, we hypothesized that defects in caveolar function might be a common mechanism by which BMPR2 mutations promote pulmonary vascular disease. To explore this, we isolated PECs from mice carrying heterozygous null Bmpr2 mutations (Bmpr2+/-), similar to those found in the majority of HPAH patients. We show Bmpr2+/- PECs have increased numbers and intracellular localization of caveolae and caveolar structural proteins Cav-1 and Cavin-1, and that these defects are reversed after blocking endocytosis with Dynasore. Src kinase is also constitutively activated in Bmpr2+/- PECs, and localization of Cav-1 to the plasma membrane is restored after treating Bmpr2+/- PECs with the Src kinase inhibitors PP2 and SKI606. Late outgrowth endothelial progenitor cells (LO-EPCs) isolated from HPAH patients show similar increased activation of Src kinase. Moreover, Bmpr2+/- PECs have impaired endothelial barrier function and barrier function is restored after treatment with PP2. These data suggest that heterozygous null BMPR2 mutations promote Src-dependent caveolar trafficking defects in PECs, and that this may contribute to pulmonary endothelial barrier dysfunction in HPAH patients.
  • Posted in Journal of Biological Chemistry, Publications
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