title: Dysregulation of clathrin promotes thyroid cell growth and contributes to multinodular goiter pathogenesis.
abstract: A germline mutation (A339V) in thyroid transcription factor-1 (TITF1/NKX2.1) was shown to be associated with multinodular goiter (MNG) and papillary thyroid carcinoma (PTC) pathogenesis. The overexpression of A339V TTF1 significantly promoted hormone-independent growth of the normal thyroid cells, representing a cause of MNG and/or PTC. Nevertheless, the underlying mechanism still remains unclear. In this study, we used liquid chromatography (LC)-tandem mass spectrometry (MS/MS)-based shotgun proteomics comparing the global protein expression profiles of normal thyroid cells (PCCL3) that overexpressed the wild-type or A339V TTF1 to identify key proteins implicated in this process. Proteomic pathway analysis revealed that the aberrant activation of epidermal growth factor (EGF) signaling is significantly associated with the overexpression of A339V TTF1 in PCCL3, and clathrin heavy chain (Chc) is the most significantly up-regulated protein of the pathway. Intriguingly, dysregulated Chc expression facilitated a nuclear accumulation of pStat3, leading to an enhanced cell proliferation of the A339V clones. Down-regulation and abrogation of Chc-mediated cellular trafficking, respectively, by knocking-down Chc and ectopic expression of a dominant-negative (DN) form of Chc could significantly reduce the nuclear pStat3 and rescue the aberrant cell proliferation of the A339V clones. Subsequent expression analysis further revealed that CHC and pSTAT3 are co-overexpressed in 66.7% (10/15) MNG. Taken together, our results suggest that the A339V TTF1 mutant protein up-regulates the cellular expression of Chc, resulting in a constitutive activation of Stat3 pathway, and prompting the aberrant growth of thyroid cells. This extensive growth signal may promote the development of MNG.
authors.affiliation: Department of Surgery, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Sin-Ting
authors.initials: ST
authors.lastname: Lau
authors.affiliation: Department of Surgery, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Tingwen
authors.initials: T
authors.lastname: Zhou
authors.affiliation: Department of Surgery, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Jessica Ai-Jia
authors.initials: JA
authors.lastname: Liu
authors.affiliation: Department of Chemistry, University of Hong Kong, Pokfulam, Hong Kong; State Key Laboratory of Synthetic Chemistry, Chemical Biology Centre, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Eva Yi-Man
authors.initials: EY
authors.lastname: Fung
authors.affiliation: Department of Chemistry, University of Hong Kong, Pokfulam, Hong Kong; State Key Laboratory of Synthetic Chemistry, Chemical Biology Centre, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
authors.affiliation: Department of Surgery, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Brian Hung-Hin
authors.initials: BH
authors.lastname: Lang
authors.affiliation: Department of Surgery, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong. Electronic address: engan@hku.hk.
authors.forename: Elly Sau-Wai
authors.initials: ES
authors.lastname: Ngan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D019556:COS Cells; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002291:Carcinoma, Papillary; D049109:Cell Proliferation / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000473:pathology; D002478:Cells, Cultured; D002648:Child; D002522:Chlorocebus aethiops; D033922:Clathrin Heavy Chains / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006044:Goiter, Nodular / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077273:Thyroid Cancer, Papillary; D013961:Thyroid Gland / Q000166:cytology* / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D055815:Young Adult
chemical_list: D033922:Clathrin Heavy Chains
keywords: Multinodular goiter; Proliferation; Proteomics; TTF1