The ubiquitin ligase Mindbomb 1 coordinates gastrointestinal secretory cell maturation
Benjamin J. Capoccia, … , Massimo Rugge, Jason C. Mills
Benjamin J. Capoccia, … , Massimo Rugge, Jason C. Mills
Published March 8, 2013
Citation Information: J Clin Invest. 2013;123(4):1475-1491. https://doi.org/10.1172/JCI65703.
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Research Article Gastroenterology

The ubiquitin ligase Mindbomb 1 coordinates gastrointestinal secretory cell maturation

Abstract

After cell fate specification, differentiating cells must amplify the specific subcellular features required for their specialized function. How cells regulate such subcellular scaling is a fundamental unanswered question. Here, we show that the E3 ubiquitin ligase Mindbomb 1 (MIB1) is required for the apical secretory apparatus established by gastric zymogenic cells as they differentiate from their progenitors. When Mib1 was deleted, death-associated protein kinase–1 (DAPK1) was rerouted to the cell base, microtubule-associated protein 1B (MAP1B) was dephosphorylated, and the apical vesicles that normally support mature secretory granules were dispersed. Consequently, secretory granules did not mature. The transcription factor MIST1 bound the first intron of Mib1 and regulated its expression. We further showed that loss of MIB1 and dismantling of the apical secretory apparatus was the earliest quantifiable aberration in zymogenic cells undergoing transition to a precancerous metaplastic state in mouse and human stomach. Our results reveal a mechanistic pathway by which cells can scale up a specific, specialized subcellular compartment to alter function during differentiation and scale it down during disease.

Authors

Benjamin J. Capoccia, Ramon U. Jin, Young-Yun Kong, Richard M. Peek Jr., Matteo Fassan, Massimo Rugge, Jason C. Mills

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Figure 3

MIB1 maintains apical compartment physiology by regulating the subcellular localization of DAPK1.

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MIB1 maintains apical compartment physiology by regulating the subcellul...
(A) Immunohistochemistry using anti-MIB1 antibodies was performed on stomach sections from Mib1Δ/Δ and control (Ctrl) mice 2 weeks after initiation of tamoxifen treatment. Neck, transition, and base zones are indicated. PCR analysis of MIB1 transcript levels and Western blot analysis of MIB1 protein levels in Mib1Δ/Δ and control ZCs are also shown. (B) Fluorescent microscopy of individual gastric units (thick dashed outline) from Mib1Δ/Δ and control mice, 2 weeks after tamoxifen treatment, stained for MIB1 (green; top) and with GSII and DAPK1 (red and green, respectively; bottom). Enlarged views (×1.5-fold) of representative ZCs (solid outline) are shown in the insets. Thin dashed outlines denote nuclei (Hoechst, blue). Note the basal subnuclear distribution of DAPK1 in Mib1Δ/Δ ZCs compared with the apical localization in control mice. (C) Gastric units stained for GSII (red) and phosphorylated MAP1B (green). (D and E) Gastric units stained for CI-M6PR (D; green) or for cathepsin L (E; green). Enlarged views (×1.5-fold) of representative ZCs are shown in the insets. Western blot for pro–cathepsin L and activated cathepsin L is also shown in E. (F) Gastric units stained for galectin 8 (green; top) and with galectin 8 and GIF (green and red, respectively; bottom). Enlarged views (×1.5-fold) of representative ZCs are shown in the insets. Note the accumulation of galectin 8 in the apical compartment of Mib1Δ/Δ ZCs. Scale bars: 10 μm (C–F); 20 μm (B); 40 μm (A).