Salivary complement inhibitors from mosquitoes: Structure and mechanism of action

Inhibition of the alternative pathway (AP) of complement by saliva from Anopheles mosquitoes facilitates feeding by blocking production of the anaphylatoxins C3a and C5a which activate mast cells leading to plasma extravasation, pain and itching. We have previously shown that albicin, a member of the SG7 protein family from An. albimanus blocks the AP by binding to and inhibiting the function of the C3 convertase, C3bBb. Here we show that SG7.AF, the albicin homolog from An. freeborni, has a similar potency to albicin but is more active in the presence of properdin, a plasma protein that acts to stabilize C3bBb. Conversely, albicin is highly active in the absence or presence of properdin. Albicin and SG7.AF stabilize the C3bBb complex in a form that accumulates on surface plasmon resonance (SPR) surfaces coated with properdin but SG7.AF binds with lower affinity than albicin. Albicin induces oligomerization of the complex in solution, suggesting that it is oligomerization that leads to stabilization on SPR surfaces. Anophensin, the albicin ortholog from An. stephensi, is only weakly active as an inhibitor of the AP, suggesting that the SG7 family may play a different functional role in this species and other species of the subgenus Cellia, containing the major malaria vectors in Africa and Asia. Crystal structures of albicin and SG7.AF reveal a novel four-helix bundle arrangement, that is stabilized by a N-terminal hydrogen bonding network. These structures provide insight into the SG7 family and related mosquito salivary proteins including the platelet-inhibitory 30kDa family.

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Anopheles gambiae Genome Conservation as a Resource for Rational Gene Drive Target Site Selection

Insects ◽

10.3390/insects12020097 ◽

2021 ◽

Vol 12 (2) ◽

pp. 97

Author(s):

Nace Kranjc ◽

Andrea Crisanti ◽

Tony Nolan ◽

Federica Bernardini

Keyword(s):

Anopheles Gambiae ◽

Data Storage ◽

Genomic Variation ◽

Malaria Vectors ◽

Anopheles Coluzzii ◽

Structural Constraints ◽

Gene Drive ◽

Genetic Traits ◽

A Genome ◽

Insight Into

The increase in molecular tools for the genetic engineering of insect pests and disease vectors, such as Anopheles mosquitoes that transmit malaria, has led to an unprecedented investigation of the genomic landscape of these organisms. The understanding of genome variability in wild mosquito populations is of primary importance for vector control strategies. This is particularly the case for gene drive systems, which look to introduce genetic traits into a population by targeting specific genomic regions. Gene drive targets with functional or structural constraints are highly desirable as they are less likely to tolerate mutations that prevent targeting by the gene drive and consequent failure of the technology. In this study we describe a bioinformatic pipeline that allows the analysis of whole genome data for the identification of highly conserved regions that can point at potential functional or structural constraints. The analysis was conducted across the genomes of 22 insect species separated by more than hundred million years of evolution and includes the observed genomic variation within field caught samples of Anopheles gambiae and Anopheles coluzzii, the two most dominant malaria vectors. This study offers insight into the level of conservation at a genome-wide scale as well as at per base-pair resolution. The results of this analysis are gathered in a data storage system that allows for flexible extraction and bioinformatic manipulation. Furthermore, it represents a valuable resource that could provide insight into population structure and dynamics of the species in the complex and benefit the development and implementation of genetic strategies to tackle malaria.

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Exploring Flaring Behaviour on Low Mass Stars, Solar-type Stars and the Sun

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009980 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 384-391

Author(s):

L. Doyle ◽

G. Ramsay ◽

J. G. Doyle ◽

P. F. Wyper ◽

E. Scullion ◽

...

Keyword(s):

High Energy ◽

The Sun ◽

Low Mass Stars ◽

Highly Active ◽

Rotation Phase ◽

Solar Type ◽

Low Mass ◽

Insight Into ◽

Reconnection Model ◽

High Cadence

AbstractWe report on our project to study the activity in both the Sun and low mass stars. Utilising high cadence, Hα observations of a filament eruption made using the CRISP spectropolarimeter mounted on the Swedish Solar Telescope has allowed us to determine 3D velocity maps of the event. To gain insight into the physical mechanism which drives the event we have qualitatively compared our observation to a 3D MHD reconnection model. Solar-type and low mass stars can be highly active producing flares with energies exceeding erg. Using K2 and TESS data we find no correlation between the number of flares and the rotation phase which is surprising. Our solar flare model can be used to aid our understanding of the origin of flares in other stars. By scaling up our solar model to replicate observed stellar flare energies, we investigate the conditions needed for such high energy flares.

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Chimeric Antibody-Binding Vitreoscilla Hemoglobin (VHb) Mediates Redox-Catalysis Reaction: New Insight into the Functional Role of VHb

International Journal of Biological Sciences ◽

10.7150/ijbs.2.208 ◽

2006 ◽

pp. 208-215 ◽

Cited By ~ 5

Author(s):

Yaneenart Suwanwong ◽

Malin Kvist ◽

Chartchalerm Isarankura-Na-Ayudhya ◽

Natta Tansila ◽

Leif Bulow ◽

...

Keyword(s):

Functional Role ◽

Antibody Binding ◽

Vitreoscilla Hemoglobin ◽

Chimeric Antibody ◽

Redox Catalysis ◽

Insight Into

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Comparative studies on glial markers

Journal of Experimental Biology ◽

10.1242/jeb.95.1.167 ◽

1981 ◽

Vol 95 (1) ◽

pp. 167-180

Author(s):

B. I. Roots

Keyword(s):

Manduca Sexta ◽

Comparative Studies ◽

Nervous Tissue ◽

Functional Role ◽

Functional Interactions ◽

Lower Vertebrates ◽

Fresh Insight ◽

Insight Into ◽

Biochemical Differentiation

Macromolecular markers for glial cells have been sought for a variety of reasons. One of the earliest was the need for a means of assessing the purity of cell and subcellular fractions prepared from nervous tissue. While there is still a requirement for this kind of tool, emphasis has shifted towards seeking information on biochemical differentiation among cells and their functional interactions. A brief general review will be made of glial markers and two of these, 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP) and glutamine synthetase (GS), will be considered in detail. Until recently studies of markers have been concentrated on the higher vertebrates and those on lower vertebrates and invertebrates have hardly begun. However, such comparative studies may lead to fresh insight into old problems. For example, CNP has long been regarded as a marker for myelin and oligodendrocytes but it has not been possible to attribute a functional role to it and its relation to myelination has remained obscure. The finding that it is present in the glia of a moth Manduca sexta which lacks myelin provides a stimulus for a fresh approach to the problem. Another example is provided by studies on GS. This enzyme is found in astrocyte feet and preliminary results indicate that it is localized also in the perineurial glia of Aplysia ganglia. These results lead to a reconsideration of the perennial question of the possible role of astrocyte feet in barrier mechanisms. Extension of comparative studies may not only raise new questions but also provide some answers.

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Palmitoylated Cysteines in Chikungunya Virus nsP1 Are Critical for Targeting to Cholesterol-Rich Plasma Membrane Microdomains with Functional Consequences for Viral Genome Replication

Journal of Virology ◽

10.1128/jvi.02183-19 ◽

2020 ◽

Vol 94 (10) ◽

Cited By ~ 3

Author(s):

William Bakhache ◽

Aymeric Neyret ◽

Eric Bernard ◽

Andres Merits ◽

Laurence Briant

Keyword(s):

Plasma Membrane ◽

Lipid Bilayers ◽

Functional Role ◽

Membrane Microdomains ◽

Genome Replication ◽

Functional Importance ◽

Late Endosomes ◽

Plasma Membrane Microdomains ◽

Insight Into

ABSTRACT In mammalian cells, alphavirus replication complexes are anchored to the plasma membrane. This interaction with lipid bilayers is mediated through the viral methyl/guanylyltransferase nsP1 and reinforced by palmitoylation of cysteine residue(s) in the C-terminal region of this protein. Lipid content of membranes supporting nsP1 anchoring remains poorly studied. Here, we explore the membrane binding capacity of nsP1 with regard to cholesterol. Using the medically important chikungunya virus (CHIKV) as a model, we report that nsP1 cosegregates with cholesterol-rich detergent-resistant membrane microdomains (DRMs), also called lipid rafts. In search for the critical factor for cholesterol partitioning, we identify nsP1 palmitoylated cysteines as major players in this process. In cells infected with CHIKV or transfected with CHIKV trans-replicase plasmids, nsP1, together with the other nonstructural proteins, are detected in DRMs. While the functional importance of CHIKV nsP1 preference for cholesterol-rich membrane domains remains to be determined, we observed that U18666A- and imipramine-induced sequestration of cholesterol in late endosomes redirected nsP1 to these compartments and simultaneously dramatically decreased CHIKV genome replication. A parallel study of Sindbis virus (SINV) revealed that nsP1 from this divergent alphavirus displays a low affinity for cholesterol and only moderately segregates with DRMs. Behaviors of CHIKV and SINV with regard to cholesterol, therefore, match with the previously reported differences in the requirement for nsP1 palmitoylation, which is dispensable for SINV but strictly required for CHIKV replication. Altogether, this study highlights the functional importance of nsP1 segregation with DRMs and provides new insight into the functional role of nsP1 palmitoylated cysteines during alphavirus replication. IMPORTANCE Functional alphavirus replication complexes are anchored to the host cell membranes through the interaction of nsP1 with the lipid bilayers. In this work, we investigate the importance of cholesterol for such an association. We show that nsP1 has affinity for cholesterol-rich membrane microdomains formed at the plasma membrane and identify conserved palmitoylated cysteine(s) in nsP1 as the key determinant for cholesterol affinity. We demonstrate that drug-induced cholesterol sequestration in late endosomes not only redirects nsP1 to this compartment but also dramatically decreases genome replication, suggesting the functional importance of nsP1 targeting to cholesterol-rich plasma membrane microdomains. Finally, we show evidence that nsP1 from chikungunya and Sindbis viruses displays different sensitivity to cholesterol sequestering agents that parallel with their difference in the requirement for nsP1 palmitoylation for replication. This research, therefore, gives new insight into the functional role of palmitoylated cysteines in nsP1 for the assembly of functional alphavirus replication complexes in their mammalian host.

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