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In Search of the Optimum Tariffs Under Third-Degree Price Discrimination
( C. W. Yang ),( S. N. Sohng ),( B. N. Huang ),( Cindy H. P. Peng ) 세종대학교 경제통합연구소 (구 세종대학교 국제경제연구소) 2006 Journal of Economic Integration Vol.21 No.1
Tariff literature on third-degree price discrimination remains only lightly explored. The purpose of the paper is to investigate whether there exist optimum tariffs in the presence of different demand elasticities. We explore (i) the case of optimum uniform ad valorem tariff, and (ii) the case of optimum discriminatory ad valorem tariffs. A two-stage optimization approach is used: profit is maximized for a foreign firm in the first stage and importing country`s optimum tariff rates are determined under maximization of welfare (sum of consumer surplus and tariff revenue). The result indicates that the optimum tariffs may not exist even with a set of well-behaved linear demand functions. Consequently, computer simulations are needed with cost and demand parameters to ensure better welfare position for home country.
c-Cbl-Mediated Neddylation Antagonizes Ubiquitination and Degradation of the TGF-β Type II Receptor
Zuo, W.,Huang, F.,Chiang, Y.,Li, M.,Du, J.,Ding, Y.,Zhang, T.,Lee, H.,Jeong, L.,Chen, Y.,Deng, H.,Feng, X.H.,Luo, S.,Gao, C.,Chen, Y.G. Cell Press 2013 Molecular cell Vol.49 No.3
Transforming growth factor β (TGF-β) is a potent antiproliferative factor in multiple types of cells. Deregulation of TGF-β signaling is associated with the development of many cancers, including leukemia, though the molecular mechanisms are largely unclear. Here, we show that Casitas B-lineage lymphoma (c-Cbl), a known proto-oncogene encoding an ubiquitin E3 ligase, promotes TGF-β signaling by neddylating and stabilizing the type II receptor (TβRII). Knockout of c-Cbl decreases the TβRII protein level and desensitizes hematopoietic stem or progenitor cells to TGF-β stimulation, while c-Cbl overexpression stabilizes TβRII and sensitizes leukemia cells to TGF-β. c-Cbl conjugates neural precursor cell-expressed, developmentally downregulated 8 (NEDD8), a ubiquitin-like protein, to TβRII at Lys556 and Lys567. Neddylation of TβRII promotes its endocytosis to EEA1-positive early endosomes while preventing its endocytosis to caveolin-positive compartments, therefore inhibiting TβRII ubiquitination and degradation. We have also identified a neddylation-activity-defective c-Cbl mutation from leukemia patients, implying a link between aberrant TβRII neddylation and leukemia development.