Identification of a Mammalian Silicon Transporter
Ratcliffe, Sarah ; Jugdaohsingh, Ravin ; Ma, Jian Feng ; Mitani-Ueno, Nakimi ; Vivancos, Julien ; Deshmukh, Rupesh ; Boekschoten, Mark ; Muller, Michael ; Mawhinney, Robert ; Marron, Alan ; Isenring, Paul ; Kinrade, Stephen ; Bélanger, Richard ; Powell, Jonathan - \ 2017
GSE58404 - Rattus norvegicus - GSE58404 - Rattus norvegicus - PRJNA252508
Silicon (Si) has long been known to play a major physiological role in certain organisms, including some sponges and many diatoms and higher plants, leading to the recent identification of multiple proteins responsible for silicon transport in a range of algal and plant species. In mammals, despite several convincing studies suggesting that silicon is an important factor in bone development and connective tissue health, there is a critical lack of understanding in biochemical pathways that enable silicon homeostasis. Here we report the identification of a mammalian efflux silicon transporter, namely Slc34a2 (also known as NaPiIIb), which was upregulated in the kidneys of rats following chronic dietary silicon deprivation. When heterologously expressed in Xenopus laevis oocytes, the protein displayed marked silicon transport activity, specifically efflux, comparable to plant OsLsi2 transfected in the same fashion and independent of sodium and/or phosphate influx. This is the first evidence for a specific active transporter protein for silicon in mammals and suggests an important role for silicon in vertebrates.
Identification of a mammalian silicon transporter
Ratcliffe, Sarah ; Jugdaohsingh, Ravin ; Vivancos, Julien ; Marron, Alan ; Deshmukh, Rupesh ; Ma, Jian Feng ; Mitani-Ueno, Namiki ; Robertson, Jack ; Wills, John ; Boekschoten, Mark V. ; Müller, Michael ; Mawhinney, Robert C. ; Kinrade, Stephen D. ; Isenring, Paul ; Bélanger, Richard R. ; Powell, Jonathan J. - \ 2017
American Journal of Physiology: Cell Physiology 312 (2017)5. - ISSN 0363-6143 - p. C550 - C561.
Rat kidneys - Silicon - Slc34a2 - Transport - Xenopus laevis oocytes
Silicon (Si) has long been known to play a major physiological and structural role in certain organisms, including diatoms, sponges, and many higher plants, leading to the recent identification of multiple proteins responsible for Si transport in a range of algal and plant species. In mammals, despite several convincing studies suggesting that silicon is an important factor in bone development and connective tissue health, there is a critical lack of understanding about the biochemical pathways that enable Si homeostasis. Here we report the identification of a mammalian efflux Si transporter, namely Slc34a2 (also termed NaPiIIb), a known sodium-phosphate cotransporter, which was upregulated in rat kidney following chronic dietary Si deprivation. Normal rat renal epithelium demonstrated punctate expression of Slc34a2, and when the protein was heterologously expressed in Xenopus laevis oocytes, Si efflux activity (i.e., movement of Si out of cells) was induced and was quantitatively similar to that induced by the known plant Si transporter OsLsi2 in the same expression system. Interestingly, Si efflux appeared saturable over time, but it did not vary as a function of extracellular HPO2- 4 or Na- concentration, suggesting that Slc34a2 harbors a functionally independent transport site for Si operating in the reverse direction to the site for phosphate. Indeed, in rats with dietary Si depletion-induced upregulation of transporter expression, there was increased urinary phosphate excretion. This is the first evidence of an active Si transport protein in mammals and points towards an important role for Si in vertebrates and explains interactions between dietary phosphate and silicon.
Payyappallimana, U. ; Subramanian, M. ; Timoshyna, A. ; Graz, B. ; Leaman, D. ; Bussmann, R.W. ; Hariramamurthi, G. ; Shankar, D. ; Klooster, C.I.E.A. van 't; Bodeker, G. ; Sekagya, Y. ; Hemstra, W. ; Gomez, F. ; Verschuuren, B. ; Ravin, E. de; Ligare, J. ; Reid, A.M. ; Petersen, L.M. - \ 2015
In: Connecting Global Priorities: Biodiversity and Human Health World Health Organization - ISBN 9789241508537 - p. 180 - 199.
Characterization of a novel leucine-rich repeat protein antigen from group B streptococci that elicits protective immunity
Seepersaud, Ravin ; Hanniffy, Sean B. ; Mayne, Peter ; Sizer, Phil ; Page, Richard Le; Wells, Jerry M. - \ 2005
Infection and Immunity 73 (2005)3. - ISSN 0019-9567 - p. 1671 - 1683.
Group B streptococci (GBS) usually behave as commensal organisms that asymptomatically colonize the gastrointestinal and urogenital tracts of adults. However, GBS are also pathogens and the leading bacterial cause of life-threatening invasive disease in neonates. While the events leading to transmission and disease in neonates remain unclear, GBS carriage and level of colonization in the mother have been shown to be significant risk factors associated with invasive infection. Surface antigens represent ideal vaccine targets for eliciting antibodies that can act as opsonins and/or inhibit colonization and invasion. Using a genetic screen for exported proteins in GBS, we identified a gene, designated lrrG, that encodes a novel LPXTG anchored surface antigen containing leucine-rich repeat (LRR) motifs found in bacterial invasins and other members of the LRR protein family. Southern blotting showed that lrrG was present in all GBS strains tested, representing the nine serotypes, and revealed the presence of an lrrG homologue in Streptococcus pyogenes. Recombinant LrrG protein was shown in vitro to adhere to epithelial cells in a dose-dependent manner, suggesting that it may function as an adhesion factor in GBS. More importantly, immunization with recombinant LrrG elicited a strong immunoglobulin G response in CBA/ca mice and protected against lethal challenge with virulent GBS. The data presented in this report suggest that this conserved protein is a highly promising candidate antigen for use in a GBS vaccine.