Structural and Biochemical Characterization of EFhd1/Swiprosin-2, an Actin-Binding Protein in Mitochondria

Abstract

Ca2+ regulates several cellular functions, including signaling events, energy production, and cell survival. These cellular processes are mediated by Ca2+-binding proteins, such as EF-hand superfamily proteins. Among the EF-hand superfamily proteins, allograft inflammatory factor-1 (AIF-1) and swiprosin-1/EF-hand domain-containing protein 2 (EFhd2) are cytosolic actin-binding proteins. AIF-1 modulates the cytoskeleton and increases the migration of immune cells. EFhd2 is also a cytoskeletal protein implicated in immune cell activation and brain cell functions. EFhd1, a mitochondrial fraternal twin of EFhd2, mediates neuronal and pro-/pre-B cell differentiation and mitoflash activation. Although EFhd1 is important for maintaining mitochondrial morphology and energy synthesis, its mechanism of action remains unclear. Here, we report the crystal structure of the EFhd1 core domain comprising a C-terminus of a proline-rich region, two EF-hand domains, and a ligand mimic helix. Structural comparisons of EFhd1, EFhd2, and AIF-1 revealed similarities in their overall structures. In the structure of the EFhd1 core domain, two Zn2+ ions were observed at the interface of the crystal contact, suggesting the possibility of Zn2+-mediated multimerization. In addition, we found that EFhd1 has Ca2+-independent β-actin-binding and Ca2+-dependent β-actin-bundling activities. These findings suggest that EFhd1, an actin-binding and -bundling protein in the mitochondria, may contribute to the Ca2+-dependent regulation of mitochondrial morphology and energy synthesis.

Calcium bursts allow rapid reorganization of EFhD2/Swip-1 cross-linked actin networks in epithelial wound closure

“…The domain structure of Drosophila Swip-1 protein resembles its mammalian orthologs, EFhD1 (also termed Swip-2) and EFhD2 (also termed Swip-1) bearing two highly conserved EF-hands and a C-terminal coiled-coil domain (ref. 39 and Supplementary Fig. 1c ).…”

Identification of Hub Genes Associated With Clear Cell Renal Cell Carcinoma by Integrated Bioinformatics Analysis

“…EFHD1 encodes a mitochondrial inner membrane protein, acted as a calcium sensor for mitochondrial flash activation ( 43 ), and induced metabolic changes during the development of pro-/pre-B cells ( 44 ). A recent report suggested that EFHD1 may interact with β-actin for its involvement in the Ca 2+ -dependent regulation of mitochondrial morphology ( 45 ). EFHD1 was significantly downregulated in both the GSE126964 and TCGA-KIRC cohorts ( Figure 4 ) and may also have an impact on mitochondrial energy metabolism in ccRCC.…”

Lineage-Specific Differences and Regulatory Networks Governing Human Chondrocyte Development

“…EF-hand domain-containing protein 1 ( EFHD1 ) expression was significantly higher in both hESC-derived and fetal growth plate chondrocytes. EFHD1 is a calcium-binding protein localized to the inner mitochondrial membrane, previously undescribed in cartilage 52 . EFHD1 protein was localized to the cytoplasm of BMP4-treated hypertrophic chondrocytes, and hypertrophic chondrocytes in the fetal growth plates, but not in articular or epiphyseal cartilage, as predicted (Fig.…”