Exchange factors for ARF GTPases (ARF-GEFs) regulate vesicle trafficking in a variety of organisms. The Arabidopsis protein GNOM is a brefeldin A (BFA) sensitive ARF-GEF that is required for the proper polar localization of PIN1, a candidate transporter of the plant hormone auxin. Mutations in GNOM lead to developmental defects that resemble those caused by interfering with auxin transport. Both PIN1 localization and auxin transport are also sensitive to BFA. In this paper, we show that GNOM localizes to endosomes and is required for their structural integrity. We engineered a BFA-resistant version of GNOM. In plants harboring this fully functional GNOM variant, PIN1 localization and auxin transport are no longer sensitive to BFA, while trafficking of other proteins is still affected by the drug. Our results demonstrate that GNOM is required for the recycling of auxin transport components and suggest that ARF-GEFs regulate specific endosomal trafficking pathways.

Trefoil factor family (TFF) peptides promote cell migration, heal the mucosa and may suppress tumor growth. In reporter gene assays we show that aspirin (1^12 mM) evokes a six-fold up-regulation of TFF2, but not TFF1 and TFF3 transcription in human gastrointestinal cell lines. 6 h after application up-regulation of endogenous TFF2 mRNA was observed. TFF2 transcription was enhanced by indomethacin and arachidonic acid but repressed by staurosporine, suggesting mediation via protein kinase C. We mapped an aspirin responding element 3 3546 to 3 3758 bp upstream of TFF2. Upregulation of TFF2 by aspirin may partially explain the chemopreventive potential of low dose aspirin in gastrointestinal carcinogenesis. ß 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

No abstract

No abstract