The C2 and PH domains of CAPS constitute an effective PI(4,5)P2-binding unit essential for Ca2+-regulated exocytosis

Li Zhang; Lei Li; Ziqing Wei; Hao Zhou; Haowen Liu; Shen Wang; Yijing Ren; Tiankai Dai; Jiafan Wang; Zhitao Hu; Cong Ma

doi:10.1016/j.str.2023.02.004

The C₂ and PH domains of CAPS constitute an effective PI(4,5)P2-binding unit essential for Ca²⁺-regulated exocytosis

Structure. 2023 Apr 6;31(4):424-434.e6. doi: 10.1016/j.str.2023.02.004. Epub 2023 Mar 1.

Authors

Li Zhang¹, Lei Li², Ziqing Wei³, Hao Zhou¹, Haowen Liu², Shen Wang¹, Yijing Ren¹, Tiankai Dai¹, Jiafan Wang², Zhitao Hu⁴, Cong Ma⁵

Affiliations

¹ Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China.
² Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia.
³ Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China; Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
⁴ Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia. Electronic address: z.hu1@uq.edu.au.
⁵ Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China. Electronic address: cong.ma@hust.edu.cn.

PMID: 36863339
DOI: 10.1016/j.str.2023.02.004

Abstract

Ca²⁺-dependent activator proteins for secretion (CAPSs) are required for Ca²⁺-regulated exocytosis in neurons and neuroendocrine cells. CAPSs contain a pleckstrin homology (PH) domain that binds PI(4,5)P2-membrane. There is also a C₂ domain residing adjacent to the PH domain, but its function remains unclear. In this study, we solved the crystal structure of the CAPS-1 C₂PH module. The structure showed that the C₂ and PH tandem packs against one another mainly via hydrophobic residues. With this interaction, the C₂PH module exhibited enhanced binding to PI(4,5)P2-membrane compared with the isolated PH domain. In addition, we identified a new PI(4,5)P2-binding site on the C₂ domain. Disruption of either the tight interaction between the C₂ and PH domains or the PI(4,5)P2-binding sites on both domains significantly impairs CAPS-1 function in Ca²⁺-regulated exocytosis at the Caenorhabditis elegans neuromuscular junction (NMJ). These results suggest that the C₂ and PH domains constitute an effective unit to promote Ca²⁺-regulated exocytosis.

Keywords: CAPS; PI(4,5)P2; SNARE; exocytosis.

Publication types

Research Support, Non-U.S. Gov't
Research Support, N.I.H., Extramural

MeSH terms

Animals
Binding Sites
Caenorhabditis elegans / metabolism
Calcium-Binding Proteins* / chemistry
Exocytosis
Pleckstrin Homology Domains*
Protein Domains

Substances

Calcium-Binding Proteins

Grants and funding

R21 EY029450/EY/NEI NIH HHS/United States