title: Nutrient uptake by marine invertebrates: cloning and functional analysis of amino acid transporter genes in developing sea urchins (Strongylocentrotus purpuratus).
abstract: Transport of amino acids from low concentrations in seawater by marine invertebrates has been extensively studied, but few of the genes involved in this physiological process have been identified. We have characterized three amino acid transporter genes cloned from embryos of the sea urchin Strongylocentrotus purpuratus. These genes show phylogenetic proximity to classical amino acid transport systems, including Gly and B0+, and the inebriated gene (INE). Heterologous expression of these genes in frog oocytes induced a 40-fold increase in alanine transport above endogenous levels, demonstrating that these genes mediate alanine transport. Antibodies specific to one of these genes (Sp-AT1) inhibited alanine transport, confirming the physiological activity of this gene in larvae. Whole-mount antibody staining of larvae revealed expression of Sp-AT1 in the ectodermal tissues associated with amino acid transport, as independently demonstrated by autoradiographic localization of radioactive alanine. Maximum rates of alanine transport increased 6-fold during early development, from embryonic to larval stages. Analysis of gene expression during this developmental period revealed that Sp-AT1 transcript abundance remained nearly constant, while that of another transporter gene (Sp-AT2) increased 11-fold. The functional characterization of these genes establishes a molecular biological basis for amino acid transport by developmental stages of marine invertebrates.
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-0371, USA.
authors.forename: Eli
authors.initials: E
authors.lastname: Meyer
authors.forename: Donal T
authors.initials: DT
authors.lastname: Manahan
mesh_terms: D000409:Alanine / Q000378:metabolism*; D026905:Amino Acid Transport Systems / Q000235:genetics*; D000818:Animals; D003001:Cloning, Molecular; D015870:Gene Expression; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D009865:Oocytes; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D047270:Strongylocentrotus purpuratus / Q000235:genetics / Q000378:metabolism*
chemical_list: D026905:Amino Acid Transport Systems; D000409:Alanine