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Biomedical subjects

R Bettencourt

Publications and source records attributed to R Bettencourt.

7 recordsLinked to original sources
PubMed2002

Hemolin gene silencing by ds-RNA injected into Cecropia pupae is lethal to next generation embryos.

There is increasing evidence of an intimate connection between participants in the innate immune system and in development. Molecules involved in the determination of dorso-ventral polarity in Drosophila have related counterparts in the signalling pathways for immune gene activation in both insects and mammals. Hemolin from the Giant silkmoth, Hyalophora cecropia, identified as a bacteria-inducible molecule and a member of the immunoglobulin superfamily, is present as protein and transcripts in oocytes and embryos. We used RNA interference (RNAi) to investigate H. cecropia gene function in vivo and demonstrated that Hemolin is crucial for the normal development of embryos. When RNAi-females were mated, no larvae emerged from their eggs and when dissected, the eggs revealed malformed embryos. Western blot analysis confirmed the lack of Hemolin gene products. We conclude that Hemolin is necessary for development, since the silencing of Hemolin gene expression leads to embryonic lethality.

Animals↗
PubMed2000

The insect immune protein hemolin is expressed during oogenesis and embryogenesis.

Hemolin is the most abundant bacteria-induced proteins in Hyalophora cecropia hemolymph. Its structural features, both at the protein and gene level, ascribe this molecule to the immunoglobulin gene superfamily (IgSF) with particular homology to neural cell adhesion molecules. An increasing number of evidence suggest a role in immune recognition and in cell adhesion events. Hemolin is also developmentally regulated as suggested by changes in its concentration during larval and pupal ecdysis (Trenczek, T., 1998. Endogenous defense mechanisms of insects. Zoology 101, 298-315; Lanz-Mendoza, H., Faye, I., 1999. Physiological aspects of the immunoglobulin superfamily in invertebrates. Dev. Comp. Immunol. 23, 359-374). In the present study the expression of hemolin was investigated in oogenesis and in early embryogenesis. Our results reveal that hemolin is expressed in follicles and in epidermal and neural tissues of embryos.

Animals↗
PubMed1999

Evaluation of the simple calculated osteoporosis risk estimation (SCORE) in older Caucasian women: the Rancho Bernardo study.

Osteoporosis is a major health problem in older women. A risk assessment tool, the Simple Calculated Osteoporosis Risk Estimation (SCORE), has been developed to identify postmenopausal women likely to have low bone mass who should be referred for bone densitometry. The objective of this study was to calculate the sensitivity, specificity and predictive values of SCORE in a community-dwelling sample of older women. A total of 1013 postmenopausal Caucasian women aged 44-98 years provided a standard medical history including history of osteoporotic fractures and medication use. Bone mineral density (BMD) was measured at the femoral neck using dual-energy X-ray absorptiometry. In accordance with the SCORE protocol, low BMD was defined as 2 or more standard deviations below the mean BMD in healthy young women. Among these older women (mean age = 72.5 years), 67% had low BMD. Using the recommended SCORE cutpoint of 6, the sensitivity of SCORE was 98% but the specificity was only 12.5%. The positive predictive value (PPV) and negative predictive value (NPV) were 69% and 75%, respectively, meaning that all but 5.5% of the women would be recommended for bone densitometry. Increasing the cutpoint of 11, based on ethnicity and the receiver operating characteristic (ROC) curve, reduced sensitivity to 80% but improved specificity to 46%. The PPV and NPV were 75% and 53%, respectively, meaning that bone scans would not be recommended for 28% of the women. However, 13% of the women with low BMD would be missed. Analyses restricted to women <74 years of age reduced the rate of recommended bone densitometry but increased the number of women with low BMD who would be missed. We conclude that SCORE has limited value as a method for appropriately referring older ambulatory women for bone densitometry.

Absorptiometry, Photon↗
PubMed1999

Implications of hemolin glycosylation and Ca2+-binding on homophilic and cellular interactions.

Insects are useful models for the study of innate immune mechanisms because of their lack of antibodies and receptors involved in adaptive immune response. Nevertheless, hemolin cloned from moths is a soluble and membrane associated Ig-related molecule that is up-regulated during immune response [Lanz-Mendoza, H. & Faye, I. (1999) Dev. Comp. Immunol. 23, 359-374]. The hemolin monomeric form has four, pair-wise, interacting Ig-domains, forming a strongly bent horseshoe structure [Su, X.-D., Gastinel, L.N., Vaughn, D.E., Faye, I., Poon, P. & Bjorkman, P. (1998) Science 281, 991-995]. To elucidate the nature of its homophilic and cellular interactions, the glycosylation and Ca2+-binding properties of hemolin were investigated. We used Hyalophora cecropia hemolin isolated from hemolymph of bacteria-injected pupae, or produced as a recombinant protein in a baculovirus/insect cell system. Both types of hemolin contain N-acetylglucosamine and probably sialic acid, as indicated by peptide:N-glycosidase F and neuraminidase digestion and glycosylation detection by Western-blotting analysis. The N-acetylglucosamine residues on hemolin were confirmed with the use of specific lectins. In addition, hemolin was shown to specifically bind calcium when spotted onto nitrocellulose and treated as for 45Ca2+ autoradiography. Earlier studies demonstrated that hemolin can bind to hemocytes and this was tested for its dependence on calcium and carbohydrates, using hemolin-coated fluorescent microspheres. A greater level of attachment of microspheres occurred in the presence of calcium than if calcium was absent. Furthermore, this binding was inhibited by EGTA and N-acetylglucosamine or N-acetylneuraminic acid, implying that carbohydrates and calcium are crucial factors in homophilic binding and cell-adhesion events mediated by this Ig-superfamily molecule.

Animals↗
PubMed1997

Cell adhesion properties of hemolin, an insect immune protein in the Ig superfamily.

The isolation of antibacterial peptides from the giant silkmoth Hyalophora cecropia has opened the area of animal antibiotics [Boman, H. G. (1991) Cell 65, 205-207] and the study of insect immune genes has revealed striking similarities to many immune response genes in mammals [Hultmark, D. (1994) Nature 267, 116-117]. However, the molecules and mechanisms behind primordial immune recognition are not understood. One candidate for one such recognition molecule is hemolin, a 48-kDa immunoglobulin-related protein first isolated from H. cecropia, where it is up-regulated upon infection and secreted into the hemolymph. Hemolin was shown to bind to bacteria and to hemocytes, giving rise to changes in hemocyte adhesiveness and intracellular phosphorylation patterns [Faye, I. & Kanost, M. (1997) in Molecular mechanisms of immune responses in insects (Brey, P. T. & Hultmark, D., eds) Chapman and Hall, London]. In the present publication, we give evidence for the presence of a 52-kDa membrane form of hemolin on hemocytes, based on flow-activated cell sorting and membrane protein extractions. In addition we reveal calcium-dependent homophilic binding properties of hemolin, using hemolin-coated microspheres. When biotinylated recombinant hemolin was allowed to bind to hemocyte membranes, higher molecular-mass complexes were formed. Furthermore, we used immunological methods and Northern-blot analysis to demonstrate the presence of hemolin in embryos and retinal discs, suggesting that hemolin is expressed in several tissues at different developmental stages. These results show novel cell adhesion features of hemolin, corroborating its multifunctional character with putative roles in cellular and humoral immunity and in development.

Amino Acid Sequence↗
PubMed1996

Regulation of the insect immune response: the effect of hemolin on cellular immune mechanisms.

Hemolin is a bacteria-inducible protein of the immunoglobulin superfamily identified in the silk moth Hyalophora cecropia. The role of this protein, in hemocyte aggregation and phagocytosis, was studied in vitro. Hemocyte aggregation, stimulated by phorbol myristate acetate or lipopolysaccharide (LPS), was prevented by hemolin in a dose-dependent fashion, but hemolin did not disrupt aggregates once they had been formed. Furthermore, hemolin was able to stimulate phagocytic activity in both hemocytes and hemocytic mbn-2 cells and this activity was enhanced by LPS. The enhanced phagocytosis produced by a combination of hemolin and LPS was prevented by the protein kinase C (PKC) inhibitors staurosporine and H-7, and PKC activity in hemocyte crude extracts was enhanced by hemolin and LPS, with the highest activity observed in the presence of both. Hemolin affected tyrosine phosphorylation of hemocyte proteins, enhancing the phosphorylation of two proteins of 20 and 30 kDa and preventing tyrosine phosphorylation of two proteins of 35 and 40 kDa. These results suggest that hemolin is involved in the regulation of the cellular immune responses via a pathway that includes PKC activation and protein tyrosine phosphorylation.

Animals↗