Spectrin-based skeleton as an actor in cell signaling

This review focuses on the recent advances in functions of spectrins in non-erythroid cells. We discuss new data concerning the commonly known role of the spectrin-based skeleton in control of membrane organization, stability and shape, and tethering protein mosaics to the cellular motors and to all major filament systems. Particular effort has been undertaken to highlight recent advances linking spectrin to cell signaling phenomena and its participation in signal transduction pathways in many cell types

Structural basis of the filamin A actin-binding domain interaction with F-actin

Cryo-EM reconstructions were deposited in the Electron Microscopy Data Bank with the following accession numbers: F20-F-actin-FLNaABD, EMD-7833; F20-F-actin-FLNaABD-Q170P, EMD-7832; F20-F-actin-FLNaABD-E254K, EMD-8918; Krios-F-actin-FLNaABD-E254K, EMD-7831. The corresponding FLNaABD-E254K filament model was deposited in the PDB with accession number 6D8C. Source data for F-actin-targeting analyses (Figs. 2c,d,g,h, 3b,c,e,f, 4d,e, 5c,d, and 6a,b) and co-sedimentation assays (Figs. 5g and 6d) are available with the paper online. Other data are available from the corresponding author upon reasonable request. We thank Z. Razinia for generating numerous FLNa constructs, S. Wu for expertise in using the Krios microscope, J. Lees for advice on model refinement, and M. Lemmon for helpful comments in preparing the manuscript. We also thank the Yale Center for Research Computing for guidance and use of the Farnam Cluster, as well as the staff at the YMS Center for Molecular Imaging for the use of the EM Core Facility. This work was funded by grants from the National Institutes of Health (R01-GM068600 (D.A.C.), R01-NS093704 (D.A.C.), R37-GM057247 (C.V.S.), R01-GM110530 (C.V.S.), T32-GM007324, T32-GM008283) and an award from American Heart Association (15PRE25700119 (D.V.I.)).Peer reviewedPostprin

A protease cascade regulates release of the human malaria parasite Plasmodium falciparum from host red blood cells

Malaria parasites replicate within a parasitophorous vacuole in red blood cells (RBCs). Progeny merozoites egress upon rupture of first the parasitophorous vacuole membrane (PVM), then poration and rupture of the RBC membrane (RBCM). Egress is protease-dependent1, but none of the effector molecules that mediate membrane rupture have been identified and it is unknown how sequential rupture of the two membranes is controlled. Minutes before egress, the parasite serine protease SUB1 is discharged into the parasitophorous vacuole2,3,4,5,6 where it cleaves multiple substrates2,5,7,8,9 including SERA6, a putative cysteine protease10,11,12. Here, we show that Plasmodium falciparum parasites lacking SUB1 undergo none of the morphological transformations that precede egress and fail to rupture the PVM. In contrast, PVM rupture and RBCM poration occur normally in SERA6-null parasites but RBCM rupture does not occur. Complementation studies show that SERA6 is an enzyme that requires processing by SUB1 to function. RBCM rupture is associated with SERA6-dependent proteolytic cleavage within the actin-binding domain of the major RBC cytoskeletal protein β-spectrin. We conclude that SUB1 and SERA6 play distinct, essential roles in a coordinated proteolytic cascade that enables sequential rupture of the two bounding membranes and culminates in RBCM disruption through rapid, precise, SERA6-mediated disassembly of the RBC cytoskeleton