N-linked glycosylation of the bone morphogenetic protein receptor type 2 (BMPR2) enhances ligand binding

Abstract

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 relevant in several biological contexts in normal and abnormal human physiology.

Autophagy contributes to BMP type 2 receptor degradation and development of pulmonary arterial hypertension

“…iPAH patients did not harbour mutations in the BMPR2 gene. Remarkably, a reduction in the upper band of BMPR2, which corresponds to the fully glycosylated mature form of the receptor , was observed in three out of four iPAH MVECs compared with control MVECs (Figure B). N ‐Glycosylation of BMPR2 has been shown to enhance its ability to bind BMP2 ligand .…”

“…Remarkably, a reduction in the upper band of BMPR2, which corresponds to the fully glycosylated mature form of the receptor [42,46], was observed in three out of four iPAH MVECs compared with control MVECs (Figure 4B). N-Glycosylation of BMPR2 has been shown to enhance its ability to bind BMP2 ligand [42]. Interestingly, the N126 glycosylation site has been found mutated in patients with hereditary PAH [43].…”

N-linked glycosylation of the antagonist Short gastrulation increases the functional complexity of BMP signals

“…Addition of sugar side chains as a general mechanism to regulate BMP function Several molecules that interact with BMP ligands are modified by glycans, and BMPs themselves are subject to glycan addition (Hang et al, 2014, Lowery et al, 2014, Tauscher et al, 2016. Among these molecules are proteoglycans (Guo and Wang, 2009, Häcker et al, 2005, Selleck, 2000, Tsg family proteins (Billington et al, 2011), as well as Sog/Chd (Marqués et al, 1997).…”

“…Likewise, mutation of glycosylation sites in mouse Twisted gastrulation (Tsg), an important regulator of BMP activity, reduces its binding to BMPs (Billington et al, 2011). Glycosylation also controls the secretion and folding of human BMP-2 (Hang et al, 2014), BMP receptor recognition, specificity, and binding strength (Lowery et al, 2014, Saremba et al, 2008.…”

N-linked glycosylation restricts the function of short gastrulation to bind and shuttle BMPs

“…Likewise, mutation of glycosylation sites in mouse twisted gastrulation (Tsg, also known as Twsg1), which is an important regulator of BMP activity, reduces its binding to BMPs (Billington et al, 2011). Glycosylation also controls the secretion and folding of human BMP2 (Hang et al, 2014), BMP receptor recognition, specificity and binding strength (Lowery et al, 2014;Saremba et al, 2008).…”