Original Paper

Cell Death and Differentiation (2013) 20, 321–332; doi:10.1038/cdd.2012.129; published online 12 October 2012

Phosphorylation of Atg5 by the Gadd45β–MEKK4-p38 pathway inhibits autophagy

E Keil1,6, R Höcker2,6, M Schuster2, F Essmann3, N Ueffing1,5, B Hoffman4, D A Liebermann4, K Pfeffer1, K Schulze-Osthoff3 and I Schmitz2

  1. 1Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University, Universitätsstr. 1, Düsseldorf, Germany
  2. 2Laboratory of Systems-oriented Immunology and Inflammation Research, Institute of Molecular and Clinical Immunology, Otto-von-Guericke-University Magdeburg and Department of Immune Control, Helmholtz Center for Infection Research, Braunschweig, Germany
  3. 3Interfaculty Institute for Biochemistry, University of Tübingen, Tübingen, Germany
  4. 4Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA, USA

Correspondence: Dr I Schmitz, Laboratory of Systems-oriented Immunology and Inflammation Research, Institute of Molecular and Clinical Immunology, Otto-von-Guericke-University Magdeburg and Department of Immune Control, Helmholtz Center for Infection Research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. Tel: +49 531 61813500; Fax: +49 531 61813599; E-mail: ingo.schmitz@helmholtz-hzi.de

5Current address: German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany

6These authors contributed equally to this work.

Received 19 April 2012; Revised 24 August 2012; Accepted 10 September 2012
Advance online publication 12 October 2012

Edited by H-U Simon

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Abstract

Autophagy is a lysosomal degradation pathway important for cellular homeostasis, mammalian development, cancer and immunity. Many molecular components of autophagy have been identified, but little is known about regulatory mechanisms controlling their effector functions. Here, we show that, in contrast to other p38 MAP kinase activators, the growth arrest and DNA damage 45 beta (Gadd45β)–MAPK/ERK kinase kinase 4 (MEKK4) pathway specifically directs p38 to autophagosomes. This process results in an accumulation of autophagosomes through p38-mediated inhibition of lysosome fusion. Conversely, autophagic flux is increased in p38-deficient fibroblasts and Gadd45β-deficient cells. We further identified the underlying mechanism and demonstrate that phosphorylation of the autophagy regulator autophagy-related (Atg)5 at threonine 75 through p38 is responsible for inhibition of starvation-induced autophagy. Thus, we show for the first time that Atg5 activity is controlled by phosphorylation and, moreover, that the spatial regulation of p38 by Gadd45β/MEKK4 negatively regulates the autophagic process.

Keywords:

Atg5; autophagy; Gadd45; p38; phosphorylation

Abbreviations:

ASK1, apoptosis signaling kinase 1; Atg, autophagy-related; BMDM, bone marrow-derived macrophage; Gadd45β, growth arrest and DNA damage 45 beta; GFP, green fluorescent protein; JNK, c-Jun N-terminal kinase; LC3, microtubule-associated protein 1 light chain 3; LPS, lipopolysaccharide; MAPK, mitogen-activated protein kinase; M-CSF, macrophage colony-stimulating factor; MEF, mouse embryonic fibroblast; MEKK4, MAPK/ERK kinase kinase 4; MKK, MAP kinase kinase; PE, phosphatidylethanolamine; RFP, red fluorescent protein; TLR, Toll-like receptor; WT, wild-type