title: Human antigen R-mediated mRNA stabilization is required for ultraviolet B-induced autoinduction of amphiregulin in keratinocytes.
abstract: All members of the EGF family are produced as transmembrane precursors that are proteolytically processed into soluble forms by disintegrin and metalloproteinases (ADAMs) for autocrine/paracrine pathways. In turn, the ligand-activated EGF receptor (EGFR) induces the expression of EGF family members, so-called "autoinduction." However, it is not well understood how this autoinduction occurs. In this study, we investigated the molecular mechanism of the autoinduction of amphiregulin (AREG), a member of the EGF family. We found that ultraviolet B (UVB) exposure increased the AREG mRNA level by stabilization of its mRNA in a human immortalized keratinocyte cell line, HaCaT. The 3' UTR of AREG mRNA was responsible for binding to an mRNA-binding protein, human antigen R (HuR), and the interaction between AREG mRNA and HuR was enhanced by UVB. Inducible knockdown of HuR expression significantly decreased AREG mRNA stability. Interestingly, treatment of HaCaT cells with an EGFR inhibitor, an EGFR neutralizing antibody, or an ADAM inhibitor destabilized AREG mRNA. In the case of ADAM inhibition, administration of soluble AREG restored the mRNA level, indicating that the stabilization occurs in a shedding-dependent manner of EGFR ligands. The HuR dependence of AREG mRNA and protein expression was also confirmed in human primary keratinocytes. Taken together, we propose a novel mechanism by which HuR regulates the stability of AREG mRNA in keratinocytes after UVB exposure and suggest that targeting of HuR functions might be crucial for understanding skin cancers caused by aberrant EGF family member-EGFR signaling.
authors: Department of Biochemistry and Molecular Genetics, Ehime University, Shitsukawa, Toon, Ehime 791-0295, Japan.
authors: Hironao
authors: H
authors: Nakayama
authors: Shinji
authors: S
authors: Fukuda
authors: Natsuki
authors: N
authors: Matsushita
authors: Hisayo
authors: H
authors: Nishida-Fukuda
authors: Hirofumi
authors: H
authors: Inoue
authors: Yuji
authors: Y
authors: Shirakata
authors: Koji
authors: K
authors: Hashimoto
authors: Shigeki
authors: S
authors: Higashiyama
mesh_terms: D020413:3' Untranslated Regions; D066258:Amphiregulin; D002461:Cell Line, Transformed; D066255:EGF Family of Proteins; D051959:ELAV Proteins / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D020871:RNA Stability / Q000235:genetics / Q000528:radiation effects*; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D014466:Ultraviolet Rays
chemical_list: D020413:3' Untranslated Regions; C587848:AREG protein, human; D066258:Amphiregulin; D066255:EGF Family of Proteins; D051959:ELAV Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; C512478:EGFR protein, human; D066246:ErbB Receptors