Structural implications of Ca2+-dependent actin-bundling function of human EFhd2/Swiprosin-1

Abstract

EFhd2/Swiprosin-1 is a cytoskeletal Ca2+-binding protein implicated in Ca2+-dependent cell spreading and migration in epithelial cells. EFhd2 domain architecture includes an N-terminal disordered region, a PxxP motif, two EF-hands, a ligand mimic helix and a C-terminal coiled-coil domain. We reported previously that EFhd2 displays F-actin bundling activity in the presence of Ca2+ and this activity depends on the coiled-coil domain and direct interaction of the EFhd2 core region. However, the molecular mechanism for the regulation of F-actin binding and bundling by EFhd2 is unknown. Here, the Ca2+-bound crystal structure of the EFhd2 core region is presented and structures of mutants defective for Ca2+-binding are also described. These structures and biochemical analyses reveal that the F-actin bundling activity of EFhd2 depends on the structural rigidity of F-actin binding sites conferred by binding of the EF-hands to Ca2+. In the absence of Ca2+, the EFhd2 core region exhibits local conformational flexibility around the EF-hand domain and C-terminal linker, which retains F-actin binding activity but loses the ability to bundle F-actin. In addition, we establish that dimerisation of EFhd2 via the C-terminal coiled-coil domain, which is necessary for F-actin bundling, occurs through the parallel coiled-coil interaction.

Swiprosin-1 deficiency impairs macrophage immune response of septic mice

“…Swiprosin-1 has been reported to affect cell migration by remodeling the actin cytoskeleton (26)(27)(28). Our results showed that swiprosin-1 deletion restrained macrophage recruitment, which partly explained the attenuated proinflammatory cytokine production in the local tissues.…”

EFHD2 promotes epithelial-to-mesenchymal transition and correlates with postsurgical recurrence of stage I lung adenocarcinoma

“…Actin-binding sites are located in the three major domains of EFHD2: polyA, EF-hand, and coiled-coil domain 13 . A recent structural study indicated that the F-actin bundling activity of EFHD2 depended on the structural rigidity of F-actin binding sites in the presence of Ca 2+ , and the C-terminal coiled-coil domain of EFHD2 is necessary for F-actin bundling 44 . Our confocal microscopy assay revealed that EFHD2 increased F-actin structure and the formation of lamellipodia (Fig.…”

Swiprosin-1 Promotes Mitochondria-Dependent Apoptosis of Glomerular Podocytes via P38 MAPK Pathway in Early-Stage Diabetic Nephropathy

“…Swiprosin-1 was also expressed in immune cells such as human and primary murine mast cells [14], murine B cells, T cells [15-17], macrophages, natural killer cells [18, 19], and human peripheral blood mononuclear cells [20]. Protein atlas database indicates that swiprosin-1 is moderately expressed in human renal glomeruli but not tubules (http://www.proteinatlas.org/ENSG00000142634-$EFHD2/tissue/kidney#imid_13574299), which is consistent with the finidng of the present study that swiprosin-1 was moderately expressed in podocytes of renal glomeruli.…”

“…Swiprosin-1, also known as EF hand domain containing 2 (EFhd2), was initially identified as a novel protein in human CD8 + lymphocytes [14], and subsequently in immature, resting or activated B cells [15-17], macrophages and natural killer cells [18, 19], and non-lymphoid tissues such as the brain, spleen, lung, liver and heart [17, 20, 21]. In murine B cells, ectopic expression of swiprosin-1 was found to enhance spontaneous and B-cell receptor induced apoptosis [16, 22].…”

“…In murine B cells, ectopic expression of swiprosin-1 was found to enhance spontaneous and B-cell receptor induced apoptosis [16, 22]. In addition, swiprosin-1 was found to be involved by signaling cascades involving Ca 2+ [19, 20], protein kinase C, and nuclear factor-κB [23]. Also, swiprosin-1 was reported to be involved in the process of caspase-9-protein complexes in non-small cell lung cancer (NSCLC) cells and may promote caspase-9 activation, which may be linked to cell apoptosis [24].…”