Everolimus-eluting bioresorbable vascular scaffold in daily clinical practice: A single-centre experience.

BACKGROUND: Recent evidence has raised concerns regarding the safety of the everolimus-eluting bioresorbable vascular scaffold (E-BVS) (Absorb, Abbott Vascular, Santa Clara, CA, USA). Following these data, the use of this device has diminished in the Netherlands; however, daily practice data are limited. Therefore we studied the incidence of safety and efficacy outcomes with this device in daily clinical practice in a single large tertiary centre in the Netherlands. METHODS: All E­BVS treated patients were included in this analysis. The primary endpoint was target lesion failure (TLF), a composite of cardiac death, target vessel non-fatal myocardial infarction (TV-MI) and clinically-driven target lesion revascularisation (TLR). The secondary endpoint was the incidence of definite scaffold thrombosis. RESULTS: Between October 2013 and January 2017, 105 patients were treated with 147 E­BVS. This population contained 42 (40%) patients with diabetes mellitus and 43 (40.9%) undergoing treatment for acute coronary syndrome, and thus represents a high-risk patient cohort. Mean follow-up was 19.8 months. Intravascular imaging guidance during scaffold implantation was used in 64/105 (43.5%) patients. The primary endpoint (TLF) occurred in 3 (2.9%) patients. All-cause mortality and cardiac mortality occurred in 2 (2%) and 0 (0%) patients respectively. TV-MI occurred in 2 patients (1.9%): both were periprocedural and not related to the BVS implantation. TLR occurred in 1 patient (1.0%) during follow-up. No definite scaffold thrombosis occurred during follow-up. CONCLUSION: This single-centre study examining the real-world experience of E­BVS implantation in a high-risk population shows excellent procedural safety and long-term clinical outcomes.

IgE responses to Ascaris and mite tropomyosins are risk factors for asthma.

BACKGROUND: The relationship between helminthiases and allergy is a matter of considerable interest and research. In the tropics, house dust mite exposure, a known risk factor for asthma, is frequently concurrent with helminth infections. It remains to be defined whether infection with the common roundworm Ascaris or its bystander immunological effects influence the prevalence and pathogenesis of asthma independently of mite sensitization. OBJECTIVE: To investigate the relationship between the IgE responses to Ascaris and its purified allergens and the risk of asthma in a tropical country. METHODS: A nested case-control study was performed in 356 subjects who reported current and past asthma symptoms (asthmatics) and 435 controls that had never experienced such symptoms. They were tested for serum levels of total IgE and specific IgE to Ascaris extract, Asc s 1 (ABA-1), Asc l 3 (tropomyosin) and GST (glutathione transferase). In addition, specific IgE to Dermatophagoides pteronyssinus, Blomia tropicalis and their tropomyosins Der p 10 and Blo t 10 was measured. Sensitization was defined as a positive specific IgE result to any extract or recombinant allergen. RESULTS: Sensitization to Ascaris and D. pteronyssinus was independently associated with asthma after adjustment for age, gender, socio-economic stratum, city and other IgE levels (adjusted ORs: 2.17; 95% CI 1.37-3.42 and 2.46; 95% CI 1.54-3.92), respectively. There was also a significant association with sensitization to the highly allergenic and cross-reactive tropomyosins Asc l 3, Blo t 10 and Der p10 (aORs: 1.76; 95% CI 1.21-2.57, 1.64; 95% CI 1.14-2.35 and 1.51; 95% CI 1.02-2.24), respectively. CONCLUSION AND CLINICAL RELEVANCE: IgE responses to Ascaris are associated with asthma symptoms in a population living in the tropics. Sensitization to the cross-reactive Ascaris and mite tropomyosins partially underlies this finding. These results have potential relevance in asthma diagnosis and management.

Association between total immunoglobulin E and antibody responses to naturally acquired Ascaris lumbricoides infection and polymorphisms of immune system-related LIG4, TNFSF13B and IRS2 genes.

The 13q33-34 region harbours a susceptibility locus to Ascaris lumbricoides, although the underlying genes are unknown. Immunoglobulin (Ig)E and IgG confer protective immunity and here we sought to investigate in an endemic population whether LIG4, TNFSF13B and IRS2 genes influence IgE and IgG levels against Ascaris and the ABA-1 allergen as a putative resistance marker. Mite-allergic asthmatic patients were analysed for potential relationships between Ascaris predisposition and allergy. One thousand and sixty-four subjects from Cartagena, Colombia, were included. Single nucleotide polymorphisms (SNPs) were genotyped using TaqMan assays. Antibody levels were measured by enzyme-linked immunosorbent assay. Linear and logistic regressions were used to model effects of genotypes on antibody levels. The GG genotype of LIG4 (rs1805388) was associated with higher IgE levels to Ascaris compared with other genotypes. TNFSF13B (rs10508198) was associated positively with IgG levels against Ascaris extract and IgE levels against ABA-1. In asthmatics, IRS2 (rs2289046) was associated with high total IgE levels. Associations held up after correction by population stratification using a set of 52 ancestry markers, age, sex and disease status. There was no association with asthma or mite sensitization. In a tropical population, LIG4 and TNFSF13B polymorphisms are associated with specific IgE and IgG to Ascaris, supporting previous linkage studies implicating the 13q33 region. Our results suggest that genes protecting against parasite infections can be different to those predisposing to asthma and atopy.

Analysis of the transthyretin-like (TTL) gene family in Ostertagia ostertagi--comparison with other strongylid nematodes and Caenorhabditis elegans.

The transthyretin-like (ttl) gene family is one of the largest conserved nematode-specific gene families, coding for a group of proteins with significant sequence similarity to transthyretins (TTR) and transthyretin-related proteins (TRP). In the present study, we investigated the ttl family in Ostertagia ostertagi (a nematode of the abomasum of cattle). Mining of expressed sequence tag (EST) databases revealed the presence of at least 18 ttl genes in O. ostertagi (Oo-ttl), most of which are constitutively transcribed from the free-living, third larval stage onwards. The full-length cDNA of one of these genes (Oo-ttl-1) was amplified and cloned for recombinant expression. Western blot analysis using a specific antiserum showed that the native protein Oo-TTL-1 was highly present in the excretory-secretory (ES) products of adults of O. ostertagi. The protein was immunolocalized to the pseudocoelomic fluid of adult worms. A phylogenetic-bioinformatic analysis of all amino acid sequence data for TTL proteins from a range of strongylid nematodes showed that they could be divided into at least five different classes. This classification was based on conserved amino acids in the first TTL signature domain and the number and location of cysteine residues. The biological role(s) of the TTLs in nematode biology is still unclear. A theoretical three-dimensional model of Oo-TTL-1 indicated that it had a similar structure to TTRs (i.e., containing ß-sheets, arranged in a ß-sandwich). In contrast to TTRs, competitive binding studies using recombinant Oo-TTL-1 indicated that the protein was devoid of any hydrophobic ligand- or thyroid hormone-binding properties. Finally, combinatorial analysis by double-stranded RNA interference of five ttl genes in the free-living nematode Caenorhabditis elegans did not reveal any visible phenotypes. More information on the transcription profile and tissue distribution of TTLs in nematodes is needed to provide new insights into the biological role of this gene family.

Conservation of the European mink (Mustela lutreola): focus on reproduction and reproductive technologies.

The European mink (Mustela lutreola) is a small mammal, which belongs to the Mustelidae family (Carnivora). Earlier, the range of distribution of this species encompassed much of the European continent. During the 20th century, the numbers of European mink declined and the range of its distribution became reduced to three fragmented populations; today this species faces extinction. The urgent necessity for effective conservation efforts to protect the European mink is accepted by the governmental organizations as well as scientific communities of most European countries. In this paper, the reasons for the disappearance of European mink are reviewed and results of past conservation efforts based on captive breeding and reintroduction programmes are critically evaluated in the broad context of modern concepts of conservation genetics and reproductive biology. The data recently obtained on the reproduction and pre-implantation development of European mink and the prospects of incorporation of modern reproductive technologies into the conservation programme of this species are discussed.

Changes in major proteins in the embryonic capsule during immobilization (fixation) of the conceptus in the third week of pregnancy in the mare.

During the third week of pregnancy, the equine conceptus is enclosed within a capsule, the glycan composition of which changes at around day 16 (ovulation = day 0) when the conceptus becomes immobilized (fixed) in the uterine lumen. Our objective was to characterize the process of fixation by identifying changes in major capsule-associated proteins. Individual equine conceptuses (n = 55) were collected transcervically by uterine lavage between days 13.5 and 26.5. Major proteins extracted from capsules were compared with those in fluids from the uterus and yolk sac by SDS-PAGE. Until day 14, a major capsule-associated protein that migrated at approximately 10 kDa was identified by N-terminal sequencing as equine beta2 microglobulin (beta2M). During fixation, beta2M in the capsule underwent limited proteolysis to an approximately 8 kDa form lacking nine amino acids from the N terminus, and was subsequently degraded. Expression of beta2M mRNA was detected in the yolk-sac wall tissues and endometrium between days 13.5 and 17.5. During this period, beta2M in the capsule was evidently not part of a complex with major histocompatibility complex class 1 heavy alpha chain bands because these were undetectable in the capsule and uterine lavage. Uterocalin (p19) was detected in uterine lavage and capsule throughout fixation, but in yolk-sac fluid only before fixation. These studies indicate that intact beta2M is a major protein associated with the embryonic capsule before fixation, after which it undergoes limited proteolysis to a truncated approximately 8 kDa form that remains in the capsule after the conceptus is immobilized.

Contrasting effects of acute and chronic gastro-intestinal helminth infections on a heterologous immune response in a transgenic adoptive transfer model.

We have previously found that co-immunisation with ovalbumin (OVA) and the body fluid of the helminth Ascaris suum inhibited an OVA-specific delayed type hypersensitivity (DTH) response by reducing OVA-specific CD4+ T lymphocyte proliferation via an IL-4 independent mechanism. In the present study, we determined whether parasite infections themselves could induce similar changes to peripheral immunisation by examining the modulation of OVA-specific immune responses during acute and chronic helminth infections. Surprisingly, an acute infection with Trichinella spiralis, but not a chronic infection with Heligmosomoides polygyrus, inhibited the OVA-specific DTH reaction. Correspondingly, the T helper 1 (Th1) OVA-specific response was decreased in mice infected with T. spiralis, but not with H. polygyrus. Inhibition of the Th1 response may be a result of a shift in the Th1/Th2 balance as although both H. polygyrus and T. spiralis infected mice induced a Th2 OVA-specific response, that exhibited by T. spiralis was more potent. Furthermore, although IL-10 secretion upon OVA restimulation was similarly increased by both infections, production of this immunoregulatory cytokine may play a role in the suppression of immune responses observed with T. spiralis infection depending on the context of its release. Interestingly, analysis of the OVA-specific T lymphocyte division by carboxyfluorescein diacetate succinimidyl ester (CFSE) staining revealed that gastro-intestinal infection with the acute helminth T. spiralis, but not with chronic H. polygyrus, inhibited the systemic immune response by significantly inhibiting the antigen-specific T cell proliferation during the primary response, a mechanism similar to that observed when A. suum parasite extracts were directly mixed with the OVA during immunisation in our previous studies.

River blindness: a role for parasite retinoid-binding proteins in the generation of pathology?

A new family of fatty acid- and retinoid-binding proteins has recently been identified in nematodes. These are apparently nematode specific and have very different structures and binding characteristics to their mammalian counterparts. Retinoids have important roles in vision, tissue differentiation and repair, and can profoundly affect collagen synthesis. Binding proteins released by a parasite might therefore play a part in the generation of the skin and eye pathology seen in river blindness. They might also be involved in the formation of the subcutaneous nodules induced by this parasite.

Local lung responses following local lung challenge with recombinant lungworm antigen in systemically sensitized sheep.

BACKGROUND: Chronic mast cell-mediated inflammation may contribute significantly towards the extensive tissue remodelling that is a feature of lungworm infection in ruminants. Understanding the factors that control tissue remodelling is a necessary step toward effective management and treatment of conditions that feature such pathology. OBJECTIVE: We sought to define in a novel ovine model system, the cellular, immune and mast cell phenotypic events that occur following local lung challenge with a recombinant protein antigen, DvA-1, derived from the ruminant lungworm nematode, Dictyocaulus viviparus. METHODS: Two spatially disparate lung segments in systemically sensitized sheep were challenged on three occasions with DvA-1 (3xDVA) and two further segments were challenged with saline (3xSAL). Two months after the third challenge, one of the two segments previously repeatedly challenged with DvA-1 was challenged again with DvA-1 (3xDVA:DVA) whilst the other was challenged with saline (3xDVA:SAL). A similar protocol was followed with the saline challenged segments (3xSAL:SAL and 3xSAL:DVA). Bronchoalveolar lavage fluid (BALF) (n = 16) and tissue (n = 3) were collected after the last challenge. RESULTS: Cellular changes 24 h after the fourth challenge were characterized by an increase in the absolute numbers of neutrophils and eosinophils in BALF from 3xDVA:DVA and 3xSAL:DVA segments. Local antibody production was implied through increased levels of antibody in both 3xDVA:DVA and 3xDVA:SAL segments, with the latter being unaffected by inflammation. Levels of active transforming growth factor beta-1 (TGF-beta(1)) were significantly increased in 3xDVA:SAL segments and a trend towards an increase was apparent in 3xDVA:DVA segments. Total TGF-beta1 levels were significantly correlated with eosinophil counts in all except the 3xDVA:SAL segments. Such changes in the bronchoalveolar space were complemented by increased ratios of sheep mast cell proteinase-1 expressing cells and tryptase expressing cells, to toluidine blue positive cells in airways from 3xDVA:DVA segments. CONCLUSION: Mast cell phenotypic events occurring as a consequence of antigen challenge were limited to segments in which changes in BALF were characterized by neutrophil influx and increased local antibody production.

Mutagenic and chemical modification of the ABA-1 allergen of the nematode Ascaris: consequences for structure and lipid binding properties.

The polyprotein allergens/antigens of nematodes (NPAs) are the only lipid binding proteins known to be produced as polyproteins. Cleavage of the large polyprotein precursors at regularly spaced proteinase cleavage sites produces 10 or 11 individual protein units of approximately 15 kDa. The sequences of these units are highly diverse within and between species, but there are five absolutely or strongly conserved amino acid positions (Trp15, Gln20, Leu42, Cys64, and Cys120). We have tested the role of these signature amino acids by mutational or chemical alteration of the ABA-1 protein of Ascaris, and examined the resulting modified proteins for perturbations of their lipid binding activities and structural integrity. Substitution of Trp15 and Gln20 both affect the stability of the protein in terms of resistance to thermal or chemical denaturation, but the ligand binding function is unaffected. Mutation of Leu42, however, disrupts both the protein's structural stability and functional integrity, as does chemical disruption of the disulfide bridge formed between Cys64 and Cys120. We also find that the C-terminal, but not the N-terminal, half of the protein binds fatty acids, indicating that the binding site may be confined to this part of the protein. This also supports the idea that the NPA units are themselves derived from an ancient duplication event, and that they may comprise two functionally distinct domains.

Coordinated Muc2 and Muc3 mucin gene expression in Trichinella spiralis infection in wild-type and cytokine-deficient mice.

Mucin hypersecretion is an important component of the immune response to gastrointestinal nematode infection. Two discrete types of mucin proteins exist in the mouse intestine, secretory Muc2 and membrane-bound Muc3. We examined Muc2 and Muc3 expression in wild-type mice and mice lacking gamma interferon receptor (IFNgammaR-/-), tumor necrosis factor receptor 1 (TNFR1-/-) and interleukin 4 (IL4-/-) infected with Trichinella spiralis. Infected wild-type mice demonstrated significant goblet cell hyperplasia and increased mucin glycoprotein. In situ hybridization showed this was accompanied by increases in Muc2 and Muc3 mRNA. Total intestinal mucin protein and Muc2 and Muc3 mRNA levels were also significantly increased in cytokine-deficient mice. These data demonstrate the coordinated up-regulation of two types of mucin genes in response to T. spiralis infection and may form the basis of an innate mucosal response independent of IFN-gamma, TNF, and IL-4.

Hydrophobic ligand binding by Zn-alpha 2-glycoprotein, a soluble fat-depleting factor related to major histocompatibility complex proteins.

Zn-alpha(2)-glycoprotein (ZAG) is a member of the major histocompatibility complex (MHC) class I family of proteins and is identical in amino acid sequence to a tumor-derived lipid-mobilizing factor associated with cachexia in cancer patients. ZAG is present in plasma and other body fluids, and its natural function, like leptin's, probably lies in lipid store homeostasis. X-ray crystallography has revealed an open groove between the helices of ZAG's alpha(1) and alpha(2) domains, containing an unidentified small ligand in a position similar to that of peptides in MHC proteins (Sanchez, L. M., Chirino, A. J., and Bjorkman, P. J. (1999) Science 283, 1914-1919). Here we show, using serum-derived and bacterial recombinant protein, that ZAG binds the fluorophore-tagged fatty acid 11-(dansylamino)undecanoic acid (DAUDA) and, by competition, natural fatty acids such as arachidonic, linolenic, eicosapentaenoic, and docosahexaenoic acids. Other MHC class I-related proteins (FcRn, HFE, HLA-Cw*0702) showed no such evidence of binding. Fluorescence and isothermal calorimetry analysis showed that ZAG binds DAUDA with K(d) in the micromolar range, and differential scanning calorimetry showed that ligand binding increases the thermal stability of the protein. Addition of fatty acids to ZAG alters its intrinsic (tryptophan) fluorescence emission spectrum, providing a strong indication that ligand binds in the expected position close to a cluster of exposed tryptophan side chains in the groove. This study therefore shows that ZAG binds small hydrophobic ligands, that the natural ligand may be a polyunsaturated fatty acid, and provides a fluorescence-based method for investigating ZAG-ligand interactions.

Uterocalin, a lipocalin provisioning the preattachment equine conceptus: fatty acid and retinol binding properties, and structural characterization.

The equine conceptus is surrounded by a fibrous capsule that persists until about day 20 of pregnancy, whereupon the capsule is lost, the conceptus attaches to the endometrium and placentation proceeds. Before attachment, the endometrium secretes in abundance a protein of the lipocalin family, uterocalin. The cessation of secretion coincides with the end of the period during which the conceptus is enclosed in its capsule, suggesting that uterocalin is essential for the support of the embryo before direct contact between maternal and foetal tissues is established. Using recombinant protein and fluorescence-based assays, we show that equine uterocalin binds the fluorescent fatty acids 11-(dansylamino)undecanoic acid, dansyl-D,L-alpha-amino-octanoic acid and cis-parinaric acid, and, by competition, oleic, palmitic, arachidonic, docosahexaenoic, gamma-linolenic, cis-eicosapentaenoic and linoleic acids. Uterocalin also binds all-trans-retinol, the binding site for which is coincident or interactive with that for fatty acids. Molecular modelling and intrinsic fluorescence analysis of the wild-type protein and a Trp-->Glu mutant protein indicated that uterocalin has an unusually solvent-exposed Trp side chain projecting from its large helix directly into solvent. This feature is unusual among lipocalins and might relate to binding to, and uptake by, the trophoblast. Uterocalin therefore has the localization and binding activities for the provisioning of the equine conceptus with lipids including those essential for morphogenesis and pattern formation. The possession of a fibrous capsule surrounding the conceptus might be an ancestral condition in mammals; homologues of uterocalin might be essential for early development in marsupials and in eutherians in which there is a prolonged preimplantation period.

A surface-associated retinol- and fatty acid-binding protein (Gp-FAR-1) from the potato cyst nematode Globodera pallida: lipid binding activities, structural analysis and expression pattern.

Parasitic nematodes produce at least two structurally novel classes of small helix-rich retinol- and fatty-acid-binding proteins that have no counterparts in their plant or animal hosts and thus represent potential targets for new nematicides. Here we describe a protein (Gp-FAR-1) from the plant-parasitic nematode Globodera pallida, which is a member of the nematode-specific fatty-acid- and retinol-binding (FAR) family of proteins but localizes to the surface of this species, placing it in a strategic position for interaction with the host. Recombinant Gp-FAR-1 was found to bind retinol, cis-parinaric acid and the fluorophore-tagged lipids 11-(dansylamino)undecanoic acid and dansyl-D,L-alpha-amino-octanoic acid. The fluorescence emission characteristics of the dansylated analogues indicated that the entire ligand enters the binding cavity. Fluorescence competition experiments showed that Gp-FAR-1 binds fatty acids in the range C(11) to C(24), with optimal binding at C(15). Intrinsic fluorescence analysis of a mutant protein into which a tryptophan residue had been inserted supported computer-based predictions of the position of this residue at the protein's interior and possibly also at the binding site. Of direct relevance to plant defence systems was the observation that Gp-FAR-1 binds two lipids (linolenic and linoleic acids) that are precursors of plant defence compounds and the jasmonic acid signalling pathway. Moreover, Gp-FAR-1 was found to inhibit the lipoxygenase-mediated modification of these substrates in vitro. Thus not only does Gp-FAR-1 function as a broad-spectrum retinol- and fatty-acid-binding protein, the results are consistent with the idea that Gp-FAR-1 is involved in the evasion of primary host plant defence systems.

Molecular and immunological characterisation of a polymorphic cytosolic fatty acid binding protein from the human blood fluke of humans, Schistosoma japonicum.

Most organisms obtain their fatty acids through their diet or by de novo synthesis, but human blood flukes belonging to the genus Schistosoma lack the oxygen-dependent pathways required for the synthesis of sterols and fatty acids so they are entirely dependent on their hosts for these and other complex lipids. Fatty acid binding proteins (FABPs) of the FABP/P2/CRABP/CRBP family of beta-barrel cytosolic lipid binding proteins (cLBP) appear to be particularly important to schistosomes in the uptake, transport and compartmentalisation of host-derived fatty acids and may provide important targets for immuno- and chemotherapy. Here we describe the isolation of a set of cDNAs prepared from the Asiatic schistosome, Schistosoma japonicum, which encode two groups of cLBPs based on sequence homology and unique cDNA restriction sites. Representative clones from the two groups, one encoding a complete Sj-FABP (F10), and the other encoding a deletion mutant (F25) were characterised at the nucleic acid level by Southern and Northern hybridisation analysis, and at the protein level by immunoblotting. The presence and size of introns in the genes encoding F10 and F25 were determined and, because of the interest in the Schistosoma mansoni FABP homologue (Sm14) as a putative vaccine candidate, the immunogenicity and protective efficacy of the two proteins were also evaluated. A particularly interesting finding was the degree of Sj-FABP amino acid sequence polymorphism found to occur within the S. japonicum worm population, which appears to be greater than that described from cLBPs from vertebrates or, indeed, any other group of organisms investigated to date.

Immunopathology of intestinal helminth infection.

The relationship between intestinal pathology and immune expulsion of gastrointestinal nematodes remains controversial. Parasite expulsion is associated with intestinal pathology in several model systems and both of these phenomena are T cell dependent. However, while immune expulsion of gastrointestinal helminth parasites is usually associated with Th2 responses, the effector mechanisms directly responsible for parasite loss have not been elucidated. In contrast, the intestinal pathology observed in many other disease models closely resembles that seen in helminth infections, but has been attributed to Th1 cytokines. We have used infection with the nematode Trichinella spiralis in mice defective for cytokines to demonstrate that although parasite expulsion is indeed IL-4 dependent, contrary to expectations, the enteropathy is also regulated by IL-4. Furthermore, abrogation of severe pathology in iNOS deficient and TNF receptor defective animals does not prevent parasite expulsion. TNF and iNOS are therefore involved in intestinal pathology in nematode infections, apparently under regulation by IL-4 and Th2 mediated responses. Therefore, it appears that the IL-4-dependent protective response against the parasite operates by a mechanism other than merely the gross degradation of the parasite's environment brought about by the immune enteropathy. However, it remains important to elucidate the protective mechanisms involved in parasite expulsion, which are still unclear.

Introduction: lipid-binding proteins: novel aspects.

Lipid-binding proteins function to transport lipids across membranes and aqueous phases and act to solubilise their cargo, protect it from chemical damage and probably also to define its destination. As such, they have been adapted to carry out a broad spectrum of biological functions in addition to their classical roles in energy metabolism and the transmission or blocking of retinoid-based signalling. The set of reviews in this issue of CMLS is designed to draw attention to some newly understood aspects and principles of their biology and structure, and concentrates on the proteins involved in transport of fatty acids and retinoids.

A novel uterine lipocalin supporting pregnancy in equids.

Horses, donkeys, and therefore, probably all equids, secrete a nonglycosylated, progesterone-dependent, 19-kDa protein (P19) into the uterine lumen during early pregnancy, and significant quantities of it are taken up by the developing conceptus. Sequence analysis and structural modelling have identified P19 as a lipocalin with greatest similarity to the murine major urinary protein lipocalins. However, lack of strong identity with any particular group of lipocalins and several unusual structural features, including a unique amino acid triplet within one of the invariant domains and an unusual external tryptophan residue, classify it as a new member of the lipocalin family. P19 is therefore likely to be a transport protein involved in supporting early embryonic development. Preliminary evidence using recombinant-derived P19 and fluorescently tagged ligands suggests that it may transport a fatty acid or retinol-like molecule. Although an initial search failed to identify homologues of P19 in other mammals, they may nevertheless exist but are synthesised and secreted in much smaller quantities, making them difficult to detect. Equids appear to need particularly large quantities of the protein during early pregnancy because of the unusually late implantation in this species and the presence of a capsule surrounding the conceptus until about day 23 of gestation.

Sticky-finger interaction sites on cytosolic lipid-binding proteins?

The cytosolic lipid-binding proteins (cLBPs) comprise a large family of small (14-15 kDa) intracellular proteins involved in the transport of small lipids, including fatty acids and retinoids within cells. Their presumed function is to solubilise, protect from chemical damage and deliver to the correct destination lipids for purposes ranging from energy metabolism (e.g. fatty acids) to signalling, gene activation and cellular differentiation (e.g. retinoids and eicosanoids). It is therefore probable that cLBPs interact directly with cellular components (membranes and/or proteins) to collect and deposit their ligands, and some external features of the different cLBPs may be involved in such interactions and determine which cellular component (integral membrane or cytosolic proteins, or membranes of different lipid compositions or domain structures) with which a given cLBP will interact. Here we have focussed on a previously unrecognised feature of cLBPs which descriminates between those for which there is empiral evidence for direct interaction with membranes, and those which do not. This is a group of bulky hydrophobic amino acid side chains (e.g. tryptophans, phenylalanines, leucines) which project directly into solvent adjacent to the portal of entry and exit of the lipid ligands. Such side chains are usually found internal to proteins, but are common at sites of protein:protein or protein:membrane interactions. These 'sticky fingers' could therefore be critical to the nature and specificity of the interactions cLBPs undergo in the web of cross-traffic in lipid movements within cells.