Functional interaction between BMPR-II and Tctex-1, a light chain of Dynein, is isoform-specific and disrupted by mutations underlying primary pulmonary hypertension.
Diverse heterozygous mutations of bone morphogenetic receptor type II (BMPR-II) underlie the inherited form of the vascular disorder primary pulmonary hypertension (PPH). As yet, the molecular detail of how such defects contribute to the pathogenesis of PPH remains unclear. BMPR-II is a member of the transforming growth factor-beta cell signalling superfamily. Ligand binding induces cell surface receptor complex formation and activates a cascade of phosphorylation events of intracellular intermediaries termed Smads, which initiate transcriptional regulation. Some 30% of PPH-causing mutations localize to exon 12, which may be spliced out forming an isoform depleted of the unusually long BMPR-II cytoplasmic tail. To further elucidate the consequences of BMPR2 mutation, we sought to characterize aspects of the cytoplasmic domain function by seeking intracellular binding partners. We now report that Tctex-1, a light chain of the motor complex dynein, interacts with the cytoplasmic domain of BMPR-II and demonstrate that Tctex-1 is phosphorylated by BMPR-II, a function disrupted by PPH disease causing mutations within exon 12. Finally we show that BMPR-II and Tctex-1 co-localize to endothelium and smooth muscle within the media of pulmonary arterioles, key sites of vascular remodelling in PPH. Taken together, these data demonstrate a discrete function for the cytoplasmic domain of BMPR-II and justify further investigation of whether the interaction with and phosphorylation of Tctex-1 contributes to the pathogenesis of PPH.
Division of Medical Genetics, University of Leicester, Leicester LE1 7RH, UK.
Rajiv D
RD
Machado
Nung
N
Rudarakanchana
Carl
C
Atkinson
Julia A
JA
Flanagan
Rachel
R
Harrison
Nicholas W
NW
Morrell
Richard C
RC
Trembath
D052006:Bone Morphogenetic Protein Receptors, Type II; D004398:Dyneins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006976:Hypertension, Pulmonary / Q000235:genetics* / Q000378:metabolism; D008168:Lung / Q000378:metabolism / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D056427:t-Complex Genome Region
D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases; C498218:BMPR2 protein, human; D052006:Bone Morphogenetic Protein Receptors, Type II; D004398:Dyneins