2l5s
Solution structure of the extracellular domain of the TGF-beta type I receptor
Structural highlights
DiseaseTGFR1_HUMAN Defects in TGFBR1 are the cause of Loeys-Dietz syndrome type 1A (LDS1A) [MIM:609192; also known as Furlong syndrome or Loeys-Dietz aortic aneurysm syndrome (LDAS). LDS1 is an aortic aneurysm syndrome with widespread systemic involvement. The disorder is characterized by arterial tortuosity and aneurysms, craniosynostosis, hypertelorism, and bifid uvula or cleft palate. Other findings include exotropy, micrognathia and retrognathia, structural brain abnormalities, intellectual deficit, congenital heart disease, translucent skin, joint hyperlaxity and aneurysm with dissection throughout the arterial tree.[1] [2] [3] [4] [5] Defects in TGFBR1 are the cause of Loeys-Dietz syndrome type 2A (LDS2A) [MIM:608967. An aortic aneurysm syndrome with widespread systemic involvement. Physical findings include prominent joint laxity, easy bruising, wide and atrophic scars, velvety and translucent skin with easily visible veins, spontaneous rupture of the spleen or bowel, diffuse arterial aneurysms and dissections, and catastrophic complications of pregnancy, including rupture of the gravid uterus and the arteries, either during pregnancy or in the immediate postpartum period. LDS2 is characterized by the absence of craniofacial abnormalities with the exception of bifid uvula that can be present in some patients. Note=TGFBR1 mutation Gln-487 has been reported to be associated with thoracic aortic aneurysms and dissection (TAAD) (PubMed:16791849). This phenotype, also known as thoracic aortic aneurysms type 5 (AAT5), is distinguised from LDS2A by having aneurysms restricted to thoracic aorta. It is unclear, however, if this condition is fulfilled in individuals bearing Gln-487 mutation, that is why they are considered as LDS2A by the OMIM resource. Defects in TGFBR1 are the cause of multiple self-healing squamous epithelioma (MSSE) [MIM:132800. A disorder characterized by multiple skin tumors that undergo spontaneous regression. Tumors appear most often on sun-exposed regions, are locally invasive, and undergo spontaneous resolution over a period of months leaving pitted scars.[6] FunctionTGFR1_HUMAN Transmembrane serine/threonine kinase forming with the TGF-beta type II serine/threonine kinase receptor, TGFBR2, the non-promiscuous receptor for the TGF-beta cytokines TGFB1, TGFB2 and TGFB3. Transduces the TGFB1, TGFB2 and TGFB3 signal from the cell surface to the cytoplasm and is thus regulating a plethora of physiological and pathological processes including cell cycle arrest in epithelial and hematopoietic cells, control of mesenchymal cell proliferation and differentiation, wound healing, extracellular matrix production, immunosuppression and carcinogenesis. The formation of the receptor complex composed of 2 TGFBR1 and 2 TGFBR2 molecules symmetrically bound to the cytokine dimer results in the phosphorylation and the activation of TGFBR1 by the constitutively active TGFBR2. Activated TGFBR1 phosphorylates SMAD2 which dissociates from the receptor and interacts with SMAD4. The SMAD2-SMAD4 complex is subsequently translocated to the nucleus where it modulates the transcription of the TGF-beta-regulated genes. This constitutes the canonical SMAD-dependent TGF-beta signaling cascade. Also involved in non-canonical, SMAD-independent TGF-beta signaling pathways. For instance, TGFBR1 induces TRAF6 autoubiquitination which in turn results in MAP3K7 ubiquitination and activation to trigger apoptosis. Also regulates epithelial to mesenchymal transition through a SMAD-independent signaling pathway through PARD6A phosphorylation and activation.[7] [8] [9] [10] [11] [12] [13] Publication Abstract from PubMedTransforming growth factor beta isoforms (TGF-beta) are among the most recently evolved members of a signaling superfamily with more than 30 members. TGF-beta play vital roles in regulating cellular growth and differentiation, and they signal through a highly restricted subset of receptors known as TGF-beta type I receptor (TbetaR-I) and TGF-beta type II receptor (TbetaR-II). TGF-beta's specificity for TbetaR-I has been proposed to arise from its pre-helix extension, a five-residue loop that binds in the cleft between TGF-beta and TbetaR-II. The structure and backbone dynamics of the unbound form of the TbetaR-I extracellular domain were determined using NMR to investigate the extension's role in binding. This showed that the unbound form is highly similar to the bound form in terms of both the beta-strand framework that defines the three-finger toxin fold and the extension and its characteristic cis-Ile54-Pro55 peptide bond. The NMR data further showed that the extension and two flanking 3(10) helices are rigid on the nanosecond-to-picosecond timescale. The functional significance of several residues within the extension was investigated by binding studies and reporter gene assays in cultured epithelial cells. These demonstrated that the pre-helix extension is essential for binding, with Pro55 and Pro59 each playing a major role. These findings suggest that the pre-helix extension and its flanking prolines evolved to endow the TGF-beta signaling complex with its unique specificity, departing from the ancestral promiscuity of the bone morphogenetic protein subfamily, where the binding interface of the type I receptor is highly flexible. The TbetaR-I pre-helix extension is structurally ordered in the unbound form and its flanking prolines are essential for binding.,Zuniga JE, Ilangovan U, Mahlawat P, Hinck CS, Huang T, Groppe JC, McEwen DG, Hinck AP J Mol Biol. 2011 Sep 30;412(4):601-18. Epub 2011 Jul 29. PMID:21821041[14] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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