Elastin Peptides Signaling Relies on Neuraminidase-1-Dependent Lactosylceramide Generation

The sialidase activity of neuraminidase-1 (Neu-1) is responsible for ERK 1/2 pathway activation following binding of elastin peptide on the elastin receptor complex. In this work, we demonstrate that the receptor and lipid rafts colocalize at the plasma membrane. We also show that the disruption of these microdomains as well as their depletion in glycolipids blocks the receptor signaling. Following elastin peptide treatment, the cellular GM3 level decreases while lactosylceramide (LacCer) content increases consistently with a GM3/LacCer conversion. The use of lactose or Neu-1 siRNA blocks this process suggesting that the elastin receptor complex is responsible for this lipid conversion. Flow cytometry analysis confirms this elastin peptide-driven LacCer generation. Further, the use of a monoclonal anti-GM3 blocking antibody shows that GM3 is required for signaling. In conclusion, our data strongly suggest that Neu-1-dependent GM3/LacCer conversion is the key event leading to signaling by the elastin receptor complex. As a consequence, we propose that LacCer is an early messenger for this receptor

N-terminal amino-acid-sequence homology of storage protein-components from barley and a diploid wheat

Wild barley (Hordeum spontaneum) and the wild diploid wheat Triticum boeoticum were possibly the first plants cultivated by early man1, giving rise to the domesticated forms Hordeum vulgare L. and Triticum monococcum L. In addition, T. boeoticum may have contributed the A genome to polyploid wheats, including common bread wheat (Triticum aestivum)2 which is a hexaploid with genome composition ABD. Hordeum seems to be the older genus, having diverged from some common ancestor before the divergence of Triticum and other genera of the subtribe Triticinae3. Prolamins constitute the major storage protein fraction of both barley and wheat; they are located in the endosperm of the caryopsis and are soluble in alcohol–water solutions4. Barley and wheat prolamins (hordeins and gliadins, respectively) contain large amounts of glutamine and proline, which together make up 50–75 mol per cent of total amino acids4,5. The hordeins and gliadins are complex mixtures of components6–8 that seem to be encoded by clusters of duplicated genes that have diverged to produce many distinguishable protein components. Despite the complexity of the gliadin mixture, the components retain considerable homology in their N-terminal region9,10 and this has been reported for zeins, the prolamins of maize (Zea mays)11, as well. Here, we report that a purified C-hordein component from barley is homologous in amino acid sequence with a purified ω-gliadin component from T. monococcum at 23 of 27 residues at the N-terminus. This result is in accord with the close relationship between the two species and indicates that, despite the propensity of prolamin genes to tolerate mutations, a significant portion of their sequences can be conserved over a period of time, which, although not accurately known, probably amounts to millions of years.&nbsp