Expression and functionality of the Na+/myo-inositol cotransporter SMIT2 in rabbit kidney

Lahjouji, Karim; Aouameur, Rym; Bissonnette, Pierre; Coady, Michael J.; Bichet, Daniel G.; Lapointe, Jean‐Yves

doi:10.1016/j.bbamem.2007.01.007

Cited by 30 publications

(38 citation statements)

References 19 publications

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“…A similar assay performed in the presence of saturating MI (E) only showed equilibration of the substrate. This data is very similar to that already observed with BBMv purified from rabbit kidney (24). This species difference for SMIT2 expression in intestine is corroborated by qRT-PCR data (Fig.…”

Section: Discussionsupporting

confidence: 90%

“…Uptake of radiolabeled MI was performed as described elsewhere by a standard filtration technique (23). Transport was initiated by mixing freshly thawed BBMv with transport media in a 1:10 ratio (in mM: 200 NaCl, 0.1 MgSO 4, 300 mannitol, 50 HEPESTris pH 7, and 1 Ci/ml [ 3 H]MI) at room temperature.…”

Section: Transport Studiesmentioning

confidence: 99%

“…Total RNA was isolated from kidney cortices and intestinal mucosa from rats and rabbits by the Trizol extraction procedure. Both rabbit and rat SMIT2 mRNA were used as standards for quantification of specific mRNAs by procedures described elsewhere (23).…”

Section: Qrt-pcrmentioning

confidence: 99%

“…In a previous paper from our laboratory, BBMv purified from rabbit kidney were successfully used to characterize the luminal transport of MI (23). A similar set of experiments was thus performed to investigate MI uptake processes in the rabbit intestine.…”

Section: Transport In Intestinal Bbmvmentioning

confidence: 99%

“…Like SMIT1, SMIT2 is expressed in the brain, intestine, and kidney, and, although both systems share remarkable functional similarities (high affinities for MI, overall substrate and inhibitor specificities, and 2:1 Na ϩ -MI stoichiometry), some differences distinguish the two transport systems: unlike SMIT1, which is highly expressed in the kidney medulla, SMIT2 is predominantly found in kidney cortex where it is expressed at the apical domains of proximal tubule cells (2,23). With this cellular location, SMIT2 is believed to be responsible for the reabsorption of MI from the glomerular filtrate, a conclusion that has been supported by MI uptake studies performed both on purified rabbit kidney brush border membrane vesicles (BBMv) (23) and on a stably SMIT2-transfected cell line (MDCK-SMIT2) (2). As well, there is no evidence that SMIT2 is regulated by osmolarity conditions, which is in accordance with its cortical location in kidney.…”

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confidence: 99%

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SMIT2 mediates all myo-inositol uptake in apical membranes of rat small intestine

Aouameur¹,

Cal²,

Bissonnette³

et al. 2007

American Journal of Physiology-Gastrointestinal and Liver Physi

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Aouameur R, Da Cal S, Bissonnette P, Coady MJ, Lapointe J-Y. SMIT2 mediates all myo-inositol uptake in apical membranes of rat small intestine. Am J Physiol Gastrointest Liver Physiol 293: G1300-G1307, 2007. First published October 11, 2007; doi:10.1152/ajpgi.00422.2007.-This study presents the characterization of myo-inositol (MI) uptake in rat intestine as evaluated by use of purified membrane preparations. Three secondary active MI cotransporters have been identified; two are Na ϩ coupled (SMIT1 and SMIT2) and one is H ϩ coupled (HMIT). Through inhibition studies using selective substrates such as D-chiro-inositol (DCI, specific for SMIT2) and L-fucose (specific for SMIT1), we show that SMIT2 is exclusively responsible for apical MI transport in rat intestine; rabbit intestine appears to lack apical transport of MI. Other sugar transport systems known to be present in apical membranes, such as SGLT1 or GLUT5, lacked any significant contribution to MI uptake. Functional analysis of rat SMIT2 activity, via electrophysiological studies in Xenopus oocytes, demonstrated similarities to the activities of SMIT2 from other species (rabbit and human) displaying high affinities for MI (0.150 Ϯ 0.040 mM), DCI (0.31 Ϯ 0.06 mM), and phlorizin (Pz; 0.016 Ϯ 0.007 mM); low affinity for glucose (36 Ϯ 7 mM); and no affinity for L-fucose. Although these functional characteristics essentially confirmed those found in rat intestinal apical membranes, a unique discrepancy was seen between the two systems studied in that the affinity constant for glucose was ϳ40-fold lower in vesicles (Ki ϭ 0.94 Ϯ 0.35 mM) than in oocytes. Finally, the transport system responsible for the basolateral efflux transporter of glucose in intestine, GLUT2, did not mediate any significant radiolabeled MI uptake in oocytes, indicating that this transport system does not participate in the basolateral exit of MI from small intestine. brush border; glucose; transport; oocytes; phlorizin THE PHYSIOLOGICAL IMPORTANCE of myo-inositol (MI) is generally considered to reflect its role in signal transduction as a precursor to phosphoinositides and inositol phosphates. In addition, MI acts as a "compatible osmolyte" in specific tissues, such as brain and kidney medulla, where variations in milieu osmolarity may threaten normal cell function. In response to an increase in osmolarity, intracellular MI concentration may rise up to 500-fold above its plasma concentration of ϳ30 M (9, 11, 12), where it prevents the accumulation effects of high ionic concentrations, which leads to DNA degradation (11a). This has been well documented in brain where conditions such as trauma (30), edema and hypernatremia (26,27,38) have been shown to increase MI levels. To reach such high intracellular concentrations, secondary active transport systems are required for MI.

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Section: Discussionsupporting

confidence: 90%

Section: Transport Studiesmentioning

confidence: 99%

Section: Qrt-pcrmentioning

confidence: 99%

Section: Transport In Intestinal Bbmvmentioning

confidence: 99%

mentioning

confidence: 99%

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SMIT2 mediates all myo-inositol uptake in apical membranes of rat small intestine

Aouameur¹,

Cal²,

Bissonnette³

et al. 2007

American Journal of Physiology-Gastrointestinal and Liver Physi

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Expression of mRNA for glucose transport proteins in jejunum, liver, kidney and skeletal muscle of pigs

et al. 2009

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Although pigs are adapted to starch-rich diets and have high turnover rates of glucose, very scarce information is available on the molecular basis of glucose transport. Therefore, the present study attempted a systematic screening for the presence of mRNA of glucose transport proteins in main organs of glucose absorption, production and conservation. From the members of the solute carrier family SLC5A (sodium glucose cotransporter), the porcine jejunum was positive for SGLT1 and SGLT3, but also contained detectable levels of SGLT5. Liver contained SGLT1, SGLT5, traces of SGLT3 and, in one of five pigs, SGLT2. Kidney contained SGLT1, SGLT2, SGLT3, SGLT5 and hardly detectable levels of SGLT4. Skeletal muscle showed weak signals for SGLT3 and SGLT5. Screening for members of the SLC2A family (facilitated glucose transporter) in intestine revealed the presence of mRNA for GLUT1, GLUT2, GLUT5, GLUT7 and GLUT8, while GLUT3, GLUT4, GLUT10 and GLUT11 were also detectable. The liver contained GLUT1, GLUT2 and GLUT8 mRNA, while GLUT3, GLUT4, GLUT5, GLUT10 and GLUT11 were poorly detectable. The kidney was positive for GLUT1, GLUT2, GLUT5, GLUT8 and GLUT11, but traces of GLUT3, GLUT4 and GLUT10 could also be detected. Skeletal muscle had the strongest signal for GLUT4, while GLUT1, GLUT3, GLUT5, GLUT8, GLUT10 and GLUT11 showed weak signals. A total of 12 unique partial cDNA sequences were submitted to GenBank. In conclusion, this study provides molecular insight into the organ-specific expression of glucose transporters in pigs and thus sheds light on the way of glucose handling in this omnivorous species.

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Inverse Salt Sensitivity of Blood Pressure: Mechanisms and Potential Relevance for Prevention of Cardiovascular Disease

Felder

Gildea

et al. 2022

Curr Hypertens Rep

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Expression and functionality of the Na+/myo-inositol cotransporter SMIT2 in rabbit kidney

Cited by 30 publications

References 19 publications

SMIT2 mediates all myo-inositol uptake in apical membranes of rat small intestine

SMIT2 mediates all myo-inositol uptake in apical membranes of rat small intestine

Expression of mRNA for glucose transport proteins in jejunum, liver, kidney and skeletal muscle of pigs

Inverse Salt Sensitivity of Blood Pressure: Mechanisms and Potential Relevance for Prevention of Cardiovascular Disease

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