Vyacheslav Yurchenko

CD147 facilitates HIV-1 infection by interacting with virus-associated cyclophilin A

Cyclophilin A (CyPA) is specifically incorporated into the virions of HIV-1 and has been shown to enhance significantly an early step of cellular HIV-1 infection. Our preliminary studies implicated CD147 as a receptor for extracellular CyPA. Here, we demonstrate a role for CyPA–CD147 interaction during the early steps of HIV-1 infection. Expression of human CD147 increased infection by HIV-1 under one-cycle conditions. However, susceptibility to infection by viruses lacking CyPA (simian immunodeficiency virus or HIV-1 produced in the presence of cyclosporin A) was unaffected by CD147. Virus-associated CyPA coimmunoprecipitated with CD147 from infected cells. Antibody to CD147 inhibited HIV-1 entry as evidenced by the delay in translocation of the HIV-1 core proteins from the membrane and inhibition of viral reverse transcription. Viruses whose replication did not require CyPA (SIV or mutant HIV-1) were resistant to the inhibitory effect of anti-CD147 antibody. These results suggest that HIV-1 entry depends on an interaction between virus-associated CyPA and CD147 on a target cell.

Dealing with the family: CD147 interactions with cyclophilins

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Recently, interaction of CD147 with proteins of the cyclophilin family has been demonstrated and activity of CD147 as a signalling receptor to extarcellular cyclophilins A and B has been shown. Given that extracellular cyclophilins are potent chemotactic agents for various immune cells, further studies of the role of cyclophilin–CD147 interaction in inflammation followed. They demonstrated that agents targeting CD147 or cyclophilin had a significant anti‐inflammatory effect in animal models of acute or chronic lung diseases and rheumatoid arthritis. Here, we review the current knowledge about interactions between CD147 and cyclophilins.

Cyclophilin–CD147 interactions: a new target for anti-inflammatory therapeutics

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Among these CD147‐interacting proteins cyclophilins represent a particularly interesting class, both in terms of structural considerations and potential medical implications. CD147 has been shown to function as a signalling receptor for extracellular cyclophilins A and B and to mediate chemotactic activity of cyclophilins towards a variety of immune cells. Recent studies using in vitro and in vivo models have demonstrated a role for cyclophilin–CD147 interactions in the regulation of inflammatory responses in a number of diseases, including acute lung inflammation, rheumatoid arthritis and cardiovascular disease. Agents targeting either CD147 or cyclophilin activity showed significant anti‐inflammatory effects in experimental models, suggesting CD147–cyclophilin interactions may be a good target for new anti‐inflammatory therapeutics. Here, we review the recent literature on different aspects of cyclophilin–CD147 interactions and their role in inflammatory diseases.

Diversity and phylogeny of insect trypanosomatids: all that is hidden shall be revealed

Monoxenous trypanosomatids, which are usually regarded as benign dwellers of the insect alimentary tract, represent a relatively obscure group within the family Trypanosomatidae. This field of study has long been in disarray with the genus level taxonomy of this group remaining artificial, species criteria elusive, host specificity and occurrence poorly known, and their diversity mostly unexplored. The time has arrived to remedy this situation: a phylogenetic approach has been applied to taxa recognition and description, and a culture-independent (PCR-based) approach for detection and identification of organisms in nature has made it feasible to study the diversity of the group. Although more than 100 typing units have been discovered recently, these appear to represent a small segment of trypanosomatid biodiversity, which still remains to be uncovered.

Evolution of parasitism in kinetoplastid flagellates

Kinetoplastid protists offer a unique opportunity for studying the evolution of parasitism. While all their close relatives are either photo- or phagotrophic, a number of kinetoplastid species are facultative or obligatory parasites, supporting a hypothesis that parasitism has emerged within this group of flagellates. In this review we discuss origin and evolution of parasitism in bodonids and trypanosomatids and specific adaptations allowing these protozoa to co-exist with their hosts. We also explore the limits of biodiversity of monoxenous (one host) trypanosomatids and some features distinguishing them from their dixenous (two hosts) relatives.

SUMO modification of human XRCC4 regulates its localization and function in DNA double-strand break repair.

ABSTRACT The nonhomologous end-joining (NHEJ) pathway is responsible for rejoining the majority of double-strand breaks in mammalian cells, including the programmed breaks introduced by V(D)J recombination. The regulation of the enzymatic activities associated with this recombination pathway is still largely unknown. Here we report that human XRCC4 (for X-ray cross-complementation group 4), a protein essential for NHEJ, is subject to posttranslational protein modification. The modifier peptide, SUMO, can be added to XRCC4 both in vitro and in vivo. The site of modification is mapped to lysine 210 by using specific mutagenesis. A protein mutated such that it cannot be SUMOylated remains localized in the cytoplasm rather than accumulating in the nucleus. Cells expressing only the mutated protein are radiation sensitive and fail to complete V(D)J recombination. Genetic fusion of the SUMO sequence to the C terminus of the mutant restores nuclear localization and radiation resistance. The modification may serve a regulatory role. Our finding fits with an emerging literature associating SUMO modification with the control of the repair and recombination associated with DNA breaks.

Diversity and phylogeny of insect trypanosomatids based on small subunit rRNA genes: Polyphyly of Leptomonas and Blastocrithidia

Abstract With the aim of further investigating phylogenetic relationships in insect trypanosomatids, we have determined the sequences of small subunit rRNA genes from ten isolates, which were originally classified as Leptomonas, Blastocrithidia, and Wallaceina based on their morphology in the hosts. The inferred maximum likelihood, parsimony, and distance trees indicate that the Leptomonas and Blastocrithidia are polyphyletic, and confirm the polyphyly of Herpetomonas and Crithidia. Blastocrithidia triatoma and Leptomonas collosoma were among the earliest branching lineages among the insect trypanosomatids, while most other isolates were found within a closely related terminal clade, which also included Crithidia fasciculata. This analysis has clearly demonstrated that the morphological classification system of insect trypanosomatids does not always reflect their genetic affinities warranting its revision in the future.

Leptomonas costaricensis sp. n. (Kinetoplastea: Trypanosomatidae), a member of the novel phylogenetic group of insect trypanosomatids closely related to the genus Leishmania.

A flagellate isolated from the intestinal tract of a reduviid bug Ricolla simillima (Heteroptera) in Costa Rica was found to represent a new trypanosomatid species by the phylogenetic analysis of small subunit ribosomal RNA (SSU rRNA), glyceraldehyde phosphate dehydrogenase (GAPDH) and large subunit of RNA polymerase II (RPOIILS) genes. The phylogenetic position of this trypanosomatid, together with its typical promastigote morphology and the host identity, allowed its classification as a species that belongs to the polyphyletic genus Leptomonas. Interestingly, the new species was revealed as a member of the novel phylogenetic clade representing the closest known relative of Leishmania. With the new species used as an outgroup to root the Leishmania RPOIILS phylogenetic tree, the lineage of the Neotropical species L. enriettii was found to branch off early, and was followed by a deep split between the Old World and the remaining New World species. This tree topology supports the hypothesis that the initial transition to dixenous parasitism in this group pre-dated the continental split and that afterwards the Neotropical and the Old World groups evolved largely independently.

Cell Surface Expression of CD147/EMMPRIN Is Regulated by Cyclophilin 60

CD147, also known as extracellular matrix metalloproteinase inducer, is a regulator of matrix metalloproteinase production and also serves as a signaling receptor for extracellular cyclophilins. Previously, we demonstrated that cell surface expression of CD147 is sensitive to cyclophilin-binding drug cyclosporin A, suggesting involvement of a cyclophilin in the regulation of intracellular transport of CD147. In this report, we identify this cyclophilin as cyclophilin 60 (Cyp60), a distinct member of the cyclophilin family of proteins. CD147 co-immunoprecipitated with Cyp60, and confocal immunofluorescent microscopy revealed intracellular co-localization of Cyp60 and CD147. This interaction with Cyp60 involved proline 211 of CD147, which was shown previously to be critical for interaction between CD147 and another cyclophilin, cyclophilin A, in solution. Mutation of this proline residue abrogated co-immunoprecipitation of CD147 and Cyp60 and reduced surface expression of CD147 on the plasma membrane. Suppression of Cyp60 expression using RNA interference had an effect similar to that of cyclosporin A: reduction of cell surface expression of CD147. These results suggest that Cyp60 plays an important role in the translocation of CD147 to the cell surface. Therefore, Cyp60 may present a novel target for therapeutic interventions in diseases where CD147 functions as a pathogenic factor, such as cancer, human immunodeficiency virus infection, or rheumatoid arthritis.

Regulation of CD147 Cell Surface Expression INVOLVEMENT OF THE PROLINE RESIDUE IN THE CD147 TRANSMEMBRANE DOMAIN

CD147, also known as extracellular matrix metalloproteinase inducer, is a regulator of matrix metalloproteinase production and serves as a signaling receptor for extracellular cyclophilins. Here we demonstrate that the cell surface expression of CD147 is regulated by cyclophilins via the transmembrane domain of CD147. Solution binding experiments demonstrated that the transmembrane domain was both necessary and sufficient for CD147 binding to cyclophilin A (CypA). Treatment with cyclosporin A significantly reduced surface expression of CD147 and of CD8-CD147 fusion protein carrying the extracellular domain of CD8 fused to the transmembrane and cytoplasmic domains of CD147, but did not affect expression of CD8. Peptide binding studies demonstrated specific interaction between CypA and the proline-containing peptide from the CD147 transmembrane domain. Mutation of this proline residue reduced binding of CD147-derived peptides to CypA and also diminished transport of CD147 to the plasma membrane without reducing the total level of CD147 expression. These results suggest involvement of a cyclophilin-related protein in CD147 cell surface expression and provide molecular details for regulation of CD147 trafficking by cyclophilins.