Enhanced insulin secretion and improved glucose tolerance in mice with homozygous inactivation of the Na+K+2Cl− co-transporter 1

Alshahrani, Saeed; Fulvio, Mauricio Di

doi:10.1530/joe-12-0244

Cited by 13 publications

(29 citation statements)

References 65 publications

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“…Thus, under the experimental conditions described in the present study RVI was absent in cells lacking NKCC1 that up-regulate NKCC2, a co-transporter that does not transport water. In line with the notion that NKCC2A may not participate in cell water recovery is the observation that insulin-secreting β-cells lacking NKCC1, but expressing low levels of NKCC2, are significantly smaller when compared to those expressing both NKCC1 and NKCC2 (Alshahrani and Di Fulvio, 2012). …”

Section: Discussionmentioning

confidence: 64%

“…These data suggest that the Slc12a1 gene is responsive to osmotic stress. In line with the latter, absence of NKCC1 in β-cells results in permanent cell shrinkage and increased insulin secretion by mechanisms related to increased NKCC2 expression (Alshahrani and Di Fulvio, 2012; Alshahrani et al, 2015). NKCC1 and NKCC2 are not functionally equivalent; although both proteins transport the same ions with the same stoichiometry (Gamba et al, 2009), NKCC1 actively co-transports ~550 molecules of water per cycle (Hamann et al, 2010), whereas NKCC2 is a “dry” co-transporter; it does not transport water (Zeuthen and Macaulay, 2012).…”

Section: Introductionmentioning

confidence: 69%

“…NKCC2 is found widespread in intracellular compartments of non-epithelial cells including hypothalamic neurons (Konopacka et al, 2015), insulin-secreting β-cells (Alshahrani et al, 2012; Alshahrani and Di Fulvio, 2012), or COS7 cells in culture (Alshahrani et al, 2015). To identify the intracellular compartments in which NKCC2 is expressed in COS7, triple immunolabeling of NKCC2, integrin β2 (Iβ2), and NKCC1 was performed.…”

Section: Resultsmentioning

confidence: 99%

“…Although there is no doubt that NKCC2 is abundantly expressed in the kidney and in cell lines derived from the TALH (Eng et al, 2007) or the macula densa (Fraser et al, 2007), there is growing evidence showing relatively low levels of expression of extra-renal NKCC2. For instance, NKCC2 expression has been reported in enteric neurons (Xue et al, 2009), gastric, intestinal, endolymphatic sac, and olfactory epithelia (Akiyama et al, 2007, 2010; Nickell et al, 2007; Nishimura et al, 2009; Xue et al, 2009; Zhu et al, 2011; Ji et al, 2012), starburst amacrine cells (Gavrikov et al, 2006), chondrocytes (Bush et al, 2010), and endocrine/neuroendocrine cells including insulin secreting β-cells of the pancreas (Corless et al, 2006; Bensellam et al, 2009; Ghanaat-Pour and Sjöholm, 2009; Alshahrani et al, 2012; Alshahrani and Di Fulvio, 2012) and vasopressinergic/oxytocinergic neurons of the supraoptic and paraventricular nuclei (Hindmarch et al, 2006; Konopacka et al, 2015). …”

Section: Introductionmentioning

confidence: 99%

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Plasma Membrane Targeting of Endogenous NKCC2 in COS7 Cells Bypasses Functional Golgi Cisternae and Complex N-Glycosylation

Kursan

Almiahoub

Almutairi

et al. 2017

Front. Cell Dev. Biol.

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Na+K+2Cl− co-transporters (NKCCs) effect the electroneutral movement of Na+-K+ and 2Cl− ions across the plasma membrane of vertebrate cells. There are two known NKCC isoforms, NKCC1 (Slc12a2) and NKCC2 (Slc12a1). NKCC1 is a ubiquitously expressed transporter involved in cell volume regulation, Cl− homeostasis and epithelial salt secretion, whereas NKCC2 is abundantly expressed in kidney epithelial cells of the thick ascending loop of Henle, where it plays key roles in NaCl reabsorption and electrolyte homeostasis. Although NKCC1 and NKCC2 co-transport the same ions with identical stoichiometry, NKCC1 actively co-transports water whereas NKCC2 does not. There is growing evidence showing that NKCC2 is expressed outside the kidney, but its function in extra-renal tissues remains unknown. The present study shows molecular and functional evidence of endogenous NKCC2 expression in COS7 cells, a widely used mammalian cell model. Endogenous NKCC2 is primarily found in recycling endosomes, Golgi cisternae, Golgi-derived vesicles, and to a lesser extent in the endoplasmic reticulum. Unlike NKCC1, NKCC2 is minimally hybrid/complex N-glycosylated under basal conditions and yet it is trafficked to the plasma membrane region of hyper-osmotically challenged cells through mechanisms that require minimal complex N-glycosylation or functional Golgi cisternae. Control COS7 cells exposed to slightly hyperosmotic (~6.7%) solutions for 16 h were not shrunken, suggesting that either one or both NKCC1 and NKCC2 may participate in cell volume recovery. However, NKCC2 targeted to the plasma membrane region or transient over-expression of NKCC2 failed to rescue NKCC1 in COS7 cells where NKCC1 had been silenced. Further, COS7 cells in which NKCC1, but not NKCC2, was silenced exhibited reduced cell size compared to control cells. Altogether, these results suggest that NKCC2 does not participate in cell volume recovery and therefore, NKCC1 and NKCC2 are functionally different Na+K+2Cl− co-transporters.

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Section: Discussionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plasma Membrane Targeting of Endogenous NKCC2 in COS7 Cells Bypasses Functional Golgi Cisternae and Complex N-Glycosylation

Kursan

Almiahoub

Almutairi

et al. 2017

Front. Cell Dev. Biol.

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“…The predominant functional presence of NKCC1 relative to other Cl − loaders expressed in rodent β-cells such as Slc12a1 17, 26, 27 , some Slc4a/26a Cl − /HCO 3 – exchangers 28, 29 or any other potential Cl − extruder of the Slc12a family 30 , partially explains the depolarizing driving force of Cl − linked to insulin secretion 3, 19, 20, 31, 32 . Rat pancreatic islets express several Cl − extruders including Slc12a4 (KCC1), Slc12a6 (KCC3) and Slc12a7 (KCC4), however, these transporters appear to be enriched in glucagon-secreting α-cells.…”

Section: Introductionmentioning

confidence: 99%

The neuronal K+Cl− co-transporter 2 (Slc12a5) modulates insulin secretion

Kursan

McMillen

Beesetty

et al. 2017

Sci Rep

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Intracellular chloride concentration ([Cl−]i) in pancreatic β-cells is kept above electrochemical equilibrium due to the predominant functional presence of Cl− loaders such as the Na+K+2Cl− co-transporter 1 (Slc12a2) over Cl−extruders of unidentified nature. Using molecular cloning, RT-PCR, Western blotting, immunolocalization and in vitro functional assays, we establish that the “neuron-specific” K+Cl− co-transporter 2 (KCC2, Slc12a5) is expressed in several endocrine cells of the pancreatic islet, including glucagon secreting α-cells, but particularly in insulin-secreting β-cells, where we provide evidence for its role in the insulin secretory response. Three KCC2 splice variants were identified: the formerly described KCC2a and KCC2b along with a novel one lacking exon 25 (KCC2a-S25). This new variant is undetectable in brain or spinal cord, the only and most abundant known sources of KCC2. Inhibition of KCC2 activity in clonal MIN6 β-cells increases basal and glucose-stimulated insulin secretion and Ca2+ uptake in the presence of glibenclamide, an inhibitor of the ATP-dependent potassium (KATP)-channels, thus suggesting a possible mechanism underlying KCC2-dependent insulin release. We propose that the long-time considered “neuron-specific” KCC2 co-transporter is expressed in pancreatic islet β-cells where it modulates Ca2+-dependent insulin secretion.

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