SEMA proteiinisuperperheen tunnus on PSI domeeni (Plexiini-semaforiini-Integriini-domeeni).

 

. 2005 Jan 18;102(4):1163–1168. doi: 10.1073/pnas.0406743102

Pathogenic hantaviruses bind plexin–semaphorin–integrin domains present at the apex of inactive, bent αvβ3 integrin conformers

Tracy Raymond *,†, Elena Gorbunova *,†, Irina N Gavrilovskaya *,†,‡, Erich R Mackow *,†,‡,§

PMCID: PMC545842  PMID: 15657120

Integriinirakenteista pohjustusta

Allosteric Disulfide Bridges in Integrins: The Molecular Switches of Redox Regulation of Integrin-Mediated Cell Functions MDPI Antioxidants August 202514(8):1005 DOI:10.3390/antiox14081005 LicenseCC BY 4.0 

Structure and mechanics of integrin-based cell adhesion

M Amin Arnaout 1, Simon L Goodman 2, 

In this communication, we review the structure of integrins in their unliganded and ligand-occupied states, evaluate the conformational rearrangements associated with integrin activation, and describe the structures, conformations, and adhesion dynamics of key cytoskeleton anchoring proteins that transduce outside-in integrin signaling.

The 18 α-subunits and 8 β-subunits of integrins assemble into 24 distinct receptors in mammals and segregate into two groups, one containing and the other lacking an extra von Willebrand factor type A domain (vWFA, known as αA or αI in integrins) in their α-subunits. αA mediates divalent cation binding to extracellular ligands in αA-containing integrins [5]. αA is a GTPase-like domain in which the catalytic site at the apex is replaced with a conserved metal-ion-dependent adhesion site (MIDAS), which is occupied by a divalent cation. αA exists naturally in two conformations closed (low affinity) and open (high affinity) [6, 7]. The open form is distinguished from the closed form by inward movement of the n-terminal α1 helix, restructuring of the F-strand/α7 loop (F/α7 loop) and a two-turn downward movement of the c-terminal α7 helix (reviewed in reference [8]). These tertiary changes produce rearrangements in the three surface loops that form MIDAS, which allow occupancy of MIDAS by an acidic residue from an exogenous ligand that provides the sixth coordination site for the bound metal ion, replacing a water molecule. The closed and open states exist in an equilibrium that favors the former by a ratio of ∼10:1 [9]. Mutations that deform the c-terminal α7 helix [10], its hydrophobic contacts with the central strand [11] or that favor its downward displacement, generate high or intermediate affinity states [12].10.1016/j.ceb.2007.08.002

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The PTB domain from the actin-binding protein tensin binds the β-tail in a talin-like manner, but with lower affinity; the positively charged tyrosine pocket explains why the interaction is indifferent to tyrosine phosphorylation [43]. The recruitment of tensin is crucial in formation of fibrillar adhesions [2]. Crystal structure of the Ig-like 21 domain (IgFLN21) from the actin cross-linking homodimer filamin 1, in complex with integrin β-tail, reveals that the ser/thr-rich membrane distal segment of the β-tail forms an extended β-strand that interacts with strands C and D of IgFLN21. The binding interface extends to the NPxY-binding site of the talin head [49••], precluding the simultaneous binding of both talin and filamin to the β-tail from the same integrin molecule. This competition for binding by filamin may negatively regulate talin-induced integrin activation and may explain the known inhibitory role of filamin on cell migration [61]. 

While F3 binding to the integrin proximal β3-tail is sufficient to switch the ectodomain into the ligand-competent state, it does not mediate integrin linkage to the cytoskeleton at focal complexes [62]; a second interaction between the rod domain of talin, formed of multiple amphipathic helical bundles, and ligand-occupied integrin β-tails appears necessary [63•]. 

The structural basis of this integrin–talin rod interaction is unknown; multivalent ligand and force applied on the early matrix–integrin–talin complexes by Rho-activated actomyosin motors may expose a binding site in the β3-tail for the talin rod [52, 64].

The adapter protein paxillin, which is incorporated together with talin in early focal complexes, may link talin to the integrin α-cytoplasmic tail (see below), enhancing resistance of matrix–integrin–talin complexes to mechanical stress [65]. 

This may explain why paxillin is often found in slow moving membrane protrusions. The talin- and actin-binding protein vinculin and the focal adhesion tyrosine kinase FAK are incorporated next into focal adhesion complexes, strengthening the ECM–cytoskeleton contacts across the integrin. Cryptic vinculin binding sites (VBS) exposed in the talin rod [46], in cooperation with talin-bound actin [66], activate vinculin by destabilizing its autoinhibitory head–tail intramolecular interaction [67]. 

Co-crystal and NMR structures of talin-derived VBS peptides in complex with the D1 (Vh1) helical bundle subdomain of the vinculin head show the α-helical VBS inserting and replacing helix 1 of D1 [50, 68]. Increasing force, exerted at the adhesion site by actomyosin contractility probably exposes more talin VBSs (up to 11 sites), leading to more vinculin recruitment. 

The vinculin tail domain also interacts with paxillin leucine rich LD motifs [69]. Both interactions probably contribute to the conversion of focal complexes into focal adhesions. FAK plays an important role in signaling networks at focal contacts [70]. It is recruited to ECM-bound integrins through interaction of its c-terminal four-helical bundle FAT domain with paxillin LD motifs [71, 72]. FAK also binds, through the F1 lobe in its n-terminal FERM domain, with the integrin β-tail, an interaction that destabilizes the autoinhibitory state, thus accessing FAK to activation by Src [73]. This interaction has not been structurally characterized. 

FAK is also involved in recruiting the adaptor protein p130Cas, a primary mechanical force sensor [74••] (see below). 

Recruitment of the actin-bundling homodimer α-actinin is a later event in formation of focal adhesions [3, 75]. A cryoEM study suggests that the region between the spectrin-like α-actinin R1 and R2 repeats in the central α-actinin domain (consisting of four tandem triple-helical bundle repeats) interacts with the proximal helical integrin β-tail already complexed with the talin head, presumably by engaging the opposite side of the β-tail helix [76]. Mechanical stress, exerted by integrin ligation transmitted to the R4 repeat of α-actinin, probably swings out helix 3 from the triple-helical bundle. 

The now accessible helix inserts into the vinculin D1 subdomain in a similar manner to talin, but with an inverted orientation relative to talin, eliciting distinct activating structural changes in vinculin [47,

68]. 

Recruitment of zyxin, through a biochemically but not structurally defined n-terminal interaction with R2/3 repeats of α-actinin [77] enhances Arp2/3-independent actin assembly in focal adhesions through interactions with Ena/VASP family of proteins [78]. 

The integrin α-cytoplasmic tail is not a passive player in integrin activation or signaling. An interaction between talin and the αIIb cytoplasmic tail has been described [79] but remains structurally uncharacterized. 

Further, at least one cytosolic protein, the EF-hand containing calcium and integrin binding protein 1 (CIB1) interacts with hydrophobic residues in the membrane-proximal region of αIIb cytoplasmic tail [80] and interferes with talin binding to an αIIb-tail peptide [81], thus potentially acting as a negative regulator of talin-induced integrin activation. 

The α4 (and α9) subunits of ligand-occupied integrins also enhance integrin–cytoskeleton links formed under shear force [65], by indirectly binding to talin through the cytoskeleton adaptor paxillin. The structures of paxillin in complex with talin or the integrin α4-tail have not been determined. 

The α4-paxillin interaction is inhibited by phosphorylation of the α4-tail at the leading edge by type I PKA, which is anchored to the α4-tail [82]. This releases paxillin-mediated inhibition of Rac, thus allowing vectorial formation of lamellepodia [83]. 

Association of the a second Rap1 effector, RAPL, with the αL (CD11a) cytoplasmic tail may act cooperatively with, or perhaps independently of, talin bound to the β2-tail to activate and cluster integrins [84].

 Integrin clustering also induces activation of the T cell protein-tyrosine phosphatase (TCPTP) through its association with the integrin α1 cytoplasmic tail; TCPTP-mediated dephosphorylation of the EGF receptor asEGF receptor associated with integrin clusters inhibits anchorage-independent cell proliferation [85].

Andes viruksen käyttämäksi solureseptoriksi tunnistettu protocadheriini-1

 Jangra, R.K., Herbert, A.S., Li, R. et al. Protocadherin-1 is essential for cell entry by New World hantaviruses. Nature 563, 559–563 (2018). https://doi.org/10.1038/s41586-018-0702-1

Abstract

The zoonotic transmission of hantaviruses from their rodent hosts to humans in North and South America is associated with a severe and frequently fatal respiratory disease, hantavirus pulmonary syndrome (HPS)1,2. No specific antiviral treatments for HPS are available, and no molecular determinants of in vivo susceptibility to hantavirus infection and HPS are known. Here we identify the human asthma-associated gene protocadherin-1 (PCDH1)3,4,5,6 as an essential determinant of entry and infection in pulmonary endothelial cells by two hantaviruses that cause HPS, Andes virus (ANDV) and Sin Nombre virus (SNV). In vitro, we show that the surface glycoproteins of ANDV and SNV directly recognize the outermost extracellular repeat domain of PCDH1—a member of the cadherin superfamily7,8—to exploit PCDH1 for entry. In vivo, genetic ablation of PCDH1 renders Syrian golden hamsters highly resistant to a usually lethal ANDV challenge. Targeting PCDH1 could provide strategies to reduce infection and disease caused by New World hantaviruses.

...https://www.nature.com/articles/s41586-018-0702-1

ANDV uusinta tietoa vuodelta 2025

  Coelho R, Kehl S, Periolo N, Biondo E, Alonso D, Perez C, et al. (2025) Virological characterization of a new isolated strain of Andes virus involved in the recent person-to-person transmission outbreak reported in Argentina. PLoS Negl Trop Dis 19(6): e0013205. https://doi.org/10.1371/journal.pntd.0013205

https://www.cell.com/cms/10.1016/j.cell.2026.01.030/asset/19303c45-3f83-4144-ba0a-415a9aa8db40/main.assets/fx1.jpg

Introduction

Andes virus (ANDV), a rodent-borne New World hantavirus, causes hantavirus cardiopulmonary syndrome (HCPS) in humans, with case fatality rates reaching 40%.1 Hantaviruses are classified into Old World hantaviruses (OWHs), which cause hemorrhagic fever with renal syndrome (HFRS), and New World hantaviruses (NWHs), which cause the more frequently fatal HCPS. Human infection occurs primarily through the inhalation of aerosolized rodent saliva and excreta, although human-to-human transmission through close contact has been documented for ANDV.2,3,4 Despite the public health threat posed by ANDV, there are no approved vaccines or therapeutics.

Like other viruses of the family Hantaviridae, ANDV is an enveloped virus enclosing a tri-segmented, negative-strand RNA genome.5,6 The medium (M) segment encodes a glycoprotein precursor (GPC), which is co-translationally cleaved by signal peptidase in the endoplasmic reticulum (ER) into two glycoproteins, Gn and Gc.7 These proteins form a metastable heterodimer at neutral pH, which then oligomerizes into tetramers that form a curved lattice structure critical for virion assembly and budding.8,9 Hantavirus assembly predominantly occurs at the Golgi apparatus or plasma membrane.10,11,12 Following egress, ANDV binds to its primary receptor, protocadherin-1 (PCDH1), for entry.13 Following endocytosis, the acidic endosomal environment triggers conformational changes in the glycoprotein complex.14 This leads to the release of the class II viral fusion protein, Gc, from the Gn–Gc complex,15 allowing Gc to mediate the fusion of the viral and endosomal membranes as it transitions from the metastable prefusion conformation to the stable postfusion conformation.5,6

Gn and Gc are the only surface-exposed glycoproteins on hantavirus virions and serve as the primary targets of the neutralizing antibody response.16,17 Antibodies that cross-neutralize multiple hantaviruses have been reported,18,19 and survivors of hantavirus infection often retain long-lasting neutralizing antibody titers.20 Moreover, neutralizing antibody titers are a strong correlate of protection for both HFRS and HCPS patients.21,22,23 These observations have spurred extensive vaccine development efforts aimed at eliciting robust, long-lasting, and broadly neutralizing immune responses directed toward the Gn and Gc antigens.24,25 Notably, recombinant vesicular stomatitis viruses (rVSVs) expressing ANDV26 or Sin Nombre virus (SNV) glycoproteins27 have shown efficacy in animal models. Additionally, an ANDV M-segment-based DNA vaccine28 has demonstrated protective effects. These approaches induced cross-neutralizing antibodies and protected hamsters and rhesus macaques against lethal challenge with ANDV and SNV, respectively.

In parallel, high-throughput isolation and characterization of monoclonal antibodies have advanced our understanding of the humoral immune response to hantavirus infection.29,30,31 Structural studies using X-ray crystallography and cryo-electron tomography (cryo-ET) have provided insights into the molecular mechanisms of antibody-mediated neutralization.30,32,33,34,35 However, high-resolution structural information of antibodies in complex with Gn–Gc in their tetrameric or lattice-associated forms remains scarce.

Structural studies of authentic ANDV virions have been constrained by biosafety level 3 requirements.36 Nevertheless, significant insights have been obtained from studies of apathogenic hantaviruses, like Tula virus (TULV). In addition, investigations of OWHs, including Puumala virus (PUUV) and Hantaan virus (HTNV), have elucidated the organization of the glycoprotein lattices and the conformational arrangement of Gn and Gc.9,15,37,38,39,40 A model of the ANDV glycoprotein tetramer and lattice was subsequently generated by docking crystal structures of the ANDV Gn base tetramer and a single-chain construct of the Gn head and Gc ectodomain heterodimer in its prefusion conformation into the cryo-ET map of TULV.8 In this model, Gn resides centrally, mediating tetramerization, whereas Gc is positioned peripherally along the edge of each tetramer, mediating tetramer-tetramer interactions. However, differences in tetramer architecture between OWHs and NWHs complicate direct extrapolation to ANDV,41 and the absence of high-resolution structures of the tetramers in their native membrane environment continues to impede a comprehensive molecular understanding of ANDV architecture, function, and antibody-mediated inhibition.

Here, we demonstrate that the addition of an eVLP tag42 to the ANDV-GPC substantially enhances the production of ANDV-virus-like particles (VLPs). Purification of these VLPs enabled single-particle cryo-electron microscopy (cryo-EM) studies, allowing us to determine the structure of individual ANDV Gn–Gc tetramers to 2.35 Å resolution, as well as dimers of ANDV Gn–Gc tetramers in three related flexing conformations to 3.2, 3.4, and 3.4 Å resolution. Furthermore, we resolved the structure of the antigen-binding fragment (Fab) of ADI-65534,43 an engineered pan-hantavirus antibody, in complex with ANDV tetramers and dimers of tetramers, unexpectedly demonstrating that the full-length immunoglobulin G (IgG) is unable to cross-link neighboring tetramers. These structures reveal the molecular basis of Gn–Gc tetramer organization, lattice formation, acid-induced membrane fusion, and antibody-mediated neutralization. Additionally, immunogenicity studies of ANDV-VLPs as a self-amplifying replicon RNA (repRNA) vaccine candidate revealed improved binding—but equivalent neutralizing—antibody titers, suggesting a need to further characterize determinants of repRNA-encoded ANDV glycoprotein immunogenicity.

Orthohantavirus andesense Andes hantaviruksen taustaa aiemmilta vuosilta

 https://pubmed.ncbi.nlm.nih.gov/40523041/

Introduction

Hantaviruses (Bunyaviricetes: Elliovirales: Hantaviridae: Mammantavirinae) are enveloped, single stranded, negative sense RNA viruses with three-segmented genome. The genomic segments consist of a small segment (S), a medium segment (M), and a large segment (L), which encode the nucleocapsid (N) protein, a nonstructural protein (NSs) in some species, surface glycoproteins (Gn and Gc), and an RNA-dependent RNA polymerase (RdRp), respectively [1]. Hantaviruses are distributed worldwide and are hosted by various vertebrate animal species. Pathogenic hantaviruses are primarily associated with rodents as natural reservoirs and are classified under the genus Orthohantavirus. These viruses establish seemingly asymptomatic and chronic infections in several rodent species. The risks of viral spillover have increased due to new farming practices, climate change, the expansion of rural human settlements, and disruptions to the zoonotic interface. Additionally, rural tourism has led to travel-related cases [2–4].

Several species of orthohantaviruses are responsible for Hantavirus Pulmonary Syndrome (HPS) in the Americas and Hemorrhagic Fever with Renal Syndrome (HFRS) in Asia and Europe. HPS, first described in 1993 in the US [5], is caused by at least 24 distinct viruses [6]. In Argentina, most HPS cases are caused by 7 viruses closely related to Andes virus (ANDV), species Orthohantavirus andesense. ANDV was the first hantavirus characterised in Argentina [7]. It was associated with the long-tailed pygmy rice rat Oligoryzomys longicaudatus in the Patagonian Andean region. After human infection, the signs and symptoms of the disease can manifest after a long period of up to 40 days [8,9]. Severe cases had progressive pulmonary edema, hypoxia and hypotension; fatal cases had a severe compromise in hemodynamic function. ANDV-HPS is associated with high case-lethality rates ranging from 21–50% [10,11].

Humans generally become infected through the inhalation of aerosolized rodent excreta. Before 1996, the route of orthohantavirus transmission was considered strictly zoonotic, resulting in “dead-end” human infections [7]. However, in 1996, an ANDV-caused HPS outbreak occurred in the small city of El Bolsón and then expanded to distant cities, such as Bariloche (121 km) and Buenos Aires (1700 km), involving 16 epidemiologically linked cases. This outbreak became a focal point for orthohantavirus research because molecular and epidemiological evidence suggested person-to-person (PTP) transmission [12,13]. A larger PTP transmission outbreak that began in 2018 and involved 34 cases and was curtailed by the implementation of strict quarantine measures. In this outbreak, several individuals were identified as superspreaders, predicting the high transmission potential of this strain [10].