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Tian Y, Datta I, Yang R, Wan C, Wang B, Crisman L, He H, Brautigam CA, Li S, Shen J, Yin Q. Oligomer-to-monomer transition underlies the chaperone function of AAGAB in AP1/AP2 assembly. Proc Natl Acad Sci U S A 2023; 120:e2205199120. [PMID: 36598941 DOI: 10.1073/pnas.2205199120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Assembly of protein complexes is facilitated by assembly chaperones. Alpha and gamma adaptin-binding protein (AAGAB) is a chaperone governing the assembly of the heterotetrameric adaptor complexes 1 and 2 (AP1 and AP2) involved in clathrin-mediated membrane trafficking. Here, we found that before AP1/2 binding, AAGAB exists as a homodimer. AAGAB dimerization is mediated by its C-terminal domain (CTD), which is critical for AAGAB stability and is missing in mutant proteins found in patients with the skin disease punctate palmoplantar keratoderma type 1 (PPKP1). We solved the crystal structure of the dimerization-mediating CTD, revealing an antiparallel dimer of bent helices. Interestingly, AAGAB uses the same CTD to recognize and stabilize the γ subunit in the AP1 complex and the α subunit in the AP2 complex, forming binary complexes containing only one copy of AAGAB. These findings demonstrate a dual role of CTD in stabilizing resting AAGAB and binding to substrates, providing a molecular explanation for disease-causing AAGAB mutations. The oligomerization state transition mechanism may also underlie the functions of other assembly chaperones.
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Abstract
In this review, Soffers and Workman discuss the initial discovery of the canonical SAGA complex, the subsequent studies that have shaped our view on the internal organization of its subunits into modules, and the latest structural work that visualizes the modules and provides insights into their function. There are many large protein complexes involved in transcription in a chromatin context. However, recent studies on the SAGA coactivator complex are generating new paradigms for how the components of these complexes function, both independently and in concert. This review highlights the initial discovery of the canonical SAGA complex 23 years ago, our evolving understanding of its modular structure and the relevance of its modular nature for its coactivator function in gene regulation.
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Affiliation(s)
- Jelly H M Soffers
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
| | - Jerry L Workman
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
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Gulbranson DR, Crisman L, Lee M, Ouyang Y, Menasche BL, Demmitt BA, Wan C, Nomura T, Ye Y, Yu H, Shen J. AAGAB Controls AP2 Adaptor Assembly in Clathrin-Mediated Endocytosis. Dev Cell 2019; 50:436-446.e5. [PMID: 31353312 DOI: 10.1016/j.devcel.2019.06.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 04/29/2019] [Accepted: 06/20/2019] [Indexed: 12/26/2022]
Abstract
Multimeric adaptors are broadly involved in vesicle-mediated membrane trafficking. AP2 adaptor, in particular, plays a central role in clathrin-mediated endocytosis (CME) by recruiting cargo and clathrin to endocytic sites. It is generally thought that trafficking adaptors such as AP2 adaptor assemble spontaneously. In this work, however, we discovered that AP2 adaptor assembly is an ordered process controlled by alpha and gamma adaptin binding protein (AAGAB), an uncharacterized factor identified in our genome-wide genetic screen of CME. AAGAB guides the sequential association of AP2 subunits and stabilizes assembly intermediates. Without the assistance of AAGAB, AP2 subunits fail to form the adaptor complex, leading to their degradation. The function of AAGAB is abrogated by a mutation that causes punctate palmoplantar keratoderma type 1 (PPKP1), a human skin disease. Since other multimeric trafficking adaptors operate in an analogous manner to AP2 adaptor, their assembly likely involves a similar regulatory mechanism.
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Affiliation(s)
- Daniel R Gulbranson
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Lauren Crisman
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - MyeongSeon Lee
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Yan Ouyang
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Bridget L Menasche
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Brittany A Demmitt
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309, USA
| | - Chun Wan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Toshifumi Nomura
- Department of Dermatology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Yihong Ye
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Haijia Yu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
| | - Jingshi Shen
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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