N-linked glycosylation of the bone morphogenetic protein receptor type 2 (BMPR2) enhances ligand binding
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The bone morphogenetic protein (BMP) signaling pathway is essential for normal development and tissue homeostasis. BMP signal transduction occurs when ligands interact with a complex of type 1 and type 2 receptors to activate downstream transcription factors. It is well established that a single BMP receptor may bind multiple BMP ligands with varying affinity, and this has been largely attributed to conformation at the amino acid level. However, all three type 2 BMP receptors (BMPR2, ACVR2A/B) contain consensus N-glycosylation sites in their extracellular domains (ECDs), which could play a role in modulating interaction with ligand. Here, we show a differential pattern of N-glycosylation between BMPR2 and ACVR2A/B. Site-directed mutagenesis reveals that BMPR2 is uniquely glycosylated near its ligand binding domain and at a position that is mutated in patients with heritable pulmonary arterial hypertension. We further demonstrate using a cell-free pulldown assay that N-glycosylation of the BMPR2-ECD enhances its ability to bind BMP2 ligand but has no impact on binding by the closely-related ACVR2B. Our results illuminate a novel aspect of BMP signaling pathway mechanics and demonstrate a functional difference resulting from post-translational modification of type 2 BMP receptors. Additionally, since BMPR2 is required for several aspects of normal development and defects in its function are strongly implicated in human disease, our findings are likely to be relevant in several biological contexts in normal and abnormal human physiology.
KeywordsBone morphogenetic protein BMPR2 ACVR2A ACVR2B Activin Glycosylation Pulmonary hypertension Heritable pulmonary arterial hypertension
We gratefully acknowledge James West (Vanderbilt) for the hBMPR2 cDNA; Mark de Caestecker (Vanderbilt) for early discussions; Giuseppe Intini (HSDM) for assistance with Bmpr2 knockdown. J.W.L. and J.M.A. are recipients of the Harvard School of Dental Medicine Dean’s Scholar Award and Research Science Institute fellowship, respectively. This work was supported by the NIH/NIAMS grant R01AR055904 awarded to V.R.
Conflict of interests
The authors declare that they have no competing interests.
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