The Glycan Domain of Thrombopoietin (TPO) Acts intrans to Enhance Secretion of the Hormone and Other Cytokines

Linden, Hannah M.; Kaushansky, Kenneth

doi:10.1074/jbc.m201297200

Cited by 14 publications

(9 citation statements)

References 58 publications

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“…3D) should result from the steric intermolecular repulsion effect of glycans that prevents the protein aggregation and promotes the folding of protein [67,68]. This observation is in good agreement with previous studies [3,4,69,70].…”

Section: Insight Into the Role Of The C-terminal Domain And Glycosylasupporting

confidence: 90%

The non‐glycosylated N‐terminal domain of human thrombopoietin is a molten globule under native conditions

et al. 2019

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Human thrombopoietin (hTPO) is a primary hematopoietic growth factor that regulates megakaryocytopoiesis and platelet production. The non‐glycosylated form of 1–163 residues of hTPO (hTPO163) including the N‐terminal active site domain (1–153 residues) is a candidate for treating thrombocytopenia. However, the autoantigenicity level of hTPO163 is higher than that of the full‐length glycosylated hTPO (ghTPO332). In order to clarify the structural and physicochemical properties of hTPO163, circular dichroism (CD) and differential scanning calorimetry (DSC) analyses were performed. CD analysis indicated that hTPO163 undergoes an induced‐fit conformational change (+19.0% for helix and −16.7% for β‐strand) upon binding to the neutralizing antibody TN1 in a manner similar to the coupled folding and binding mechanism. Moreover, DSC analysis showed that the thermal transition process of hTPO163 is a multistate transition; hTPO163 is thermally stabilized upon receptor (c‐Mpl) binding, as indicated with raising the midpoint (Tm) temperature of the transition by at least +9.5 K. The conformational variability and stability of hTPO163 indicate that hTPO163 exists as a molten globule under native conditions, which may enable the induced‐fit conformational change according to the type of ligands (antibodies and receptor). Additionally, CD and computational analyses indicated that the C‐terminal domain (154–332 residues) and glycosylation assists the folding of the N‐terminal domain. These observations suggest that the antibody affinity and autoantigenicity of hTPO163 might be reduced, if the conformational variability of hTPO163 is restricted by mutation and/or by the addition of C‐terminal domain with glycosylation to keep its conformation suitable for the c‐Mpl recognition.

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Section: Insight Into the Role Of The C-terminal Domain And Glycosylasupporting

confidence: 90%

The non‐glycosylated N‐terminal domain of human thrombopoietin is a molten globule under native conditions

et al. 2019

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“…First, as it is modified with multiple sites of both N– and O–linked carbohydrate, the carboxyl‐terminal domain greatly prolongs the circulatory half‐life of the hormone (Harker et al , ). Second, the carboxyl‐terminal domain serves as an intramolecular chaperone, aiding in the proper folding of the polypeptide into the mature hormone (Linden & Kaushansky, , ; Muto et al , ).…”

Section: Structure Of Thrombopoietinmentioning

confidence: 99%

Thrombopoietin from beginning to end

2014

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SummaryIn the two decades since its cloning, thrombopoietin (TPO) has emerged not only as a critical haematopoietic cytokine, but also serves as a great example of bench-to-bedside research. Thrombopoietin, produced by the liver, is the primary regulator of megakaryocyte progenitor expansion and differentiation. Additionally, as TPO is vital for the maintenance of haematopoietic stem cells, it can truly be described as a pan-haematopoietic cytokine. Since recombinant TPO became available, the molecular mechanisms of TPO function have been the subject of extensive research. Via its receptor, c-Mpl (also termed MPL), TPO activates a wide array of downstream signalling pathways, promoting cellular survival and proliferation. Due to its central, non-redundant role in haematopoiesis, alterations of both the hormone and its receptor contribute to human disease; congenital and acquired states of thrombocytosis and thrombocytopenia and aplastic anaemia as a result from dysregulated TPO expression or functional alterations of c-Mpl. With TPO mimetics now in clinical use, the story of this haematopoietic cytokine represents a great success for biomedical research.Keywords: thrombopoeitin, megakaryocytes, megakaryocytopoiesis, myeloproliferative disease. HistoryThe term erythropoietin (EPO) was first used in the literature in 1906 to describe the humoral substance responsible for erythropoiesis. At the time, blood platelets were barely distinguishable in the best microscopes, prompting their description with the pejorative phrase 'the dust of the blood'. However, the work of Carnot and of Wright and others in the early 20th century defined the critical role of blood platelets in coagulation and their origin from the marrow megakaryocyte, ultimately leading Kelemen and Tanos (1958) to coin the term thrombopoietin (TPO, also termed THPO) to describe the humoral substance responsible for platelet production.In the mid-1960s, several groups began attempting to purify TPO from the plasma of thrombocytopenic animals. These early efforts were severely handicapped by inconvenient and insensitive assays for the hormone, and the attempts failed to produce unequivocal proof of the existence of TPO. With the availability of in vitro megakaryocyte differentiation assays in the 1980s, additional purifications were attempted; however, while some claims were made of its biological activities, attempts to produce a cDNA for TPO, the sine qua non of the existence of a protein, also failed.Occasionally in science, a finding from one field, although by itself important, can have a catalytic effect on a seemingly unrelated area of research. The discovery and characterization of the murine myeloproliferative leukaemia virus (MPLV) had such an influence on the search for TPO. The virus causes an acute myeloproliferative syndrome in infected mice (Wendling et al, 1986). In 1990, the responsible oncogene (v-mpl, now termed Mpl) was cloned, and the protooncogene (c-mpl, also now termed Mpl) obtained 2 years later (Souyri et al, 1990;Vigon et al, 19...

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“…1,2 The major TPO isoform is a 353-aa peptide containing a highly glycosylated C-terminal domain and an amino-terminal receptor binding domain (RBD) that mediates interaction with the TPO receptor (c-mpl) on hematopoietic cells. [3][4][5] TPO is encoded by the THPO gene, which maps to 3q27.1 and contains up to 6 coding exons. 6 Increased TPO production caused by gain-of-function THPO variants results in the myeloproliferative disorder thrombocythemia-1 (Online Mendelian Inheritance in Man #187950), in which the circulating platelet count is elevated, sometimes causing bleeding or thrombosis.…”

Section: Introductionmentioning

confidence: 99%