title: CUL3-KBTBD6/KBTBD7 ubiquitin ligase cooperates with GABARAP proteins to spatially restrict TIAM1-RAC1 signaling.
abstract: The small Rho GTPase RAC1 is an essential regulator of cellular signaling that controls actin rearrangements and cell motility. Here, we identify a novel CUL3 RING ubiquitin ligase complex, containing the substrate adaptors KBTBD6 and KBTBD7, that mediates ubiquitylation and proteasomal degradation of TIAM1, a RAC1-specific GEF. Increasing the abundance of TIAM1 by depletion of KBTBD6 and/or KBTBD7 leads to elevated RAC1 activity, changes in actin morphology, loss of focal adhesions, reduced proliferation, and enhanced invasion. KBTBD6 and KBTBD7 employ ATG8 family-interacting motifs to bind preferentially to GABARAP proteins. Surprisingly, ubiquitylation and degradation of TIAM1 by CUL3(KBTBD6/KBTBD7) depends on its binding to GABARAP proteins. Our study reveals that recruitment of CUL3(KBTBD6/KBTBD7) to GABARAP-containing vesicles regulates the abundance of membrane-associated TIAM1 and subsequently spatially restricted RAC1 signaling. Besides their role in autophagy and trafficking, we uncovered a previously unknown function of GABARAP proteins as membrane-localized signaling scaffolds.
authors: Institute of Biochemistry II, Goethe University School of Medicine, 60590 Frankfurt am Main, Germany.
authors: Heide Marika
authors: HM
authors: Genau
authors: Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt am Main, Germany.
authors: Jessica
authors: J
authors: Huber
authors: Department of Biology, University of Konstanz, 78464 Konstanz, Germany; Biotechnology Institute Thurgau, 8280 Kreuzlingen, Switzerland.
authors: Francesco
authors: F
authors: Baschieri
authors: Buchmann Institute for Molecular Life Sciences, Goethe University, 60438 Frankfurt am Main, Germany.
authors: Masato
authors: M
authors: Akutsu
authors: Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt am Main, Germany.
authors: Volker
authors: V
authors: Dötsch
authors: Department of Biology, University of Konstanz, 78464 Konstanz, Germany; Biotechnology Institute Thurgau, 8280 Kreuzlingen, Switzerland.
authors: Hesso
authors: H
authors: Farhan
authors: Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt am Main, Germany.
authors: Vladimir
authors: V
authors: Rogov
authors: Institute of Biochemistry II, Goethe University School of Medicine, 60590 Frankfurt am Main, Germany. Electronic address: behrends@em.uni-frankfurt.de.
authors: Christian
authors: C
authors: Behrends
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins; D000071190:Autophagy-Related Protein 8 Family; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D055503:Protein Multimerization; D015398:Signal Transduction; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000071190:Autophagy-Related Protein 8 Family; C503645:CUL3 protein, human; D044842:Cullin Proteins; C116741:GABARAP protein, human; C498698:GABARAPL2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; C000598978:KBTBD6 protein, human; C549143:KBTBD7 protein, human; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; C107953:RAC1 protein, human; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; D015534:Trans-Activators; D020830:rac1 GTP-Binding Protein