title: Involvement of l(-)-rhamnose in sea urchin gastrulation. Part II: α-l-Rhamnosidase.
abstract: The sea urchin embryo is recognized as a model system to reveal developmental mechanisms involved in human health and disease. In Part I of this series, six carbohydrates were tested for their effects on gastrulation in embryos of the sea urchin Lytechinus pictus. Only l-rhamnose caused dramatic increases in the numbers of unattached archenterons and exogastrulated archenterons in living, swimming embryos. It was found that at 30 h post-fertilization the l-rhamnose had an unusual inverse dose-dependent effect, with low concentrations (1-3 mM) interfering with development and higher concentrations (30 mM) having little to no effect on normal development. In this study, embryos were examined for inhibition of archenteron development after treatment with α-l-rhamnosidase, an endoglycosidase that removes terminal l-rhamnose sugars from glycans. It was observed that the enzyme had profound effects on gastrulation, an effect that could be suppressed by addition of l-rhamnose as a competitive inhibitor. The involvement of l-rhamnose-containing glycans in sea urchin gastrulation was unexpected, since there are no characterized biosynthetic pathways for rhamnose utilization in animals. It is possible there exists a novel l-rhamnose-containing glycan in sea urchins, or that the enzyme and sugar interfere with the function of rhamnose-binding lectins, which are components of the innate immune system in many vertebrate and invertebrate species.
authors.affiliation: Department of Biology and Center for Cancer and Developmental Biology,California State University,Northridge,California 91330-8303,USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Liang
authors.affiliation: Department of Biology and Center for Cancer and Developmental Biology,California State University,Northridge,California 91330-8303,USA.
authors.forename: Heghush
authors.initials: H
authors.lastname: Aleksanyan
authors.affiliation: Department of Biology and Center for Cancer and Developmental Biology,California State University,Northridge,California 91330-8303,USA.
authors.forename: Stan
authors.initials: S
authors.lastname: Metzenberg
authors.affiliation: Department of Biology and Center for Cancer and Developmental Biology,California State University,Northridge.18111 Nordhoff Street,Northridge,California 91330-8303,USA.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Oppenheimer
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000187:drug effects* / Q000196:embryology; D047108:Embryonic Development / Q000187:drug effects; D005260:Female; D054262:Gastrulation / Q000187:drug effects*; D006026:Glycoside Hydrolases / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D012210:Rhamnose / Q000378:metabolism / Q000494:pharmacology*; D012617:Sea Urchins / Q000187:drug effects* / Q000196:embryology; D013997:Time Factors
chemical_list: D006026:Glycoside Hydrolases; C022525:alpha-L-rhamnosidase; D012210:Rhamnose
keywords:    l-rhamnose; Archenteron development; Innate immunity; Rhamnose-binding lectin; Sea urchin gastrulation; α-l-Rhamnosidase