Calbindin-D9k and parvalbumin are exclusively located along basolateral membranes in rat distal nephron.

Abstract

There is strong evidence that vitamin D-dependent Ca(2+)-binding proteins, i.e., calbindin-D9k and calbindin-D28k, facilitate diffusion of Ca2+ through the cytosolic compartment of renal and intestinal cells, which transport Ca2+ transcellularly. In the study presented here, parvalbumin, calbindin-D9k, and calbindin-D28k were localized precisely by immunocytochemistry in rat kidney. Antisera recognizing specifically the thick ascending loop of Henle, the connecting tubules and collecting ducts, and the intercalated cells of the collecting ducts were used to identify different cell types. In rat kidney cortex, parvalbumin and calbindin-D9k colocalized in the thick ascending loop of Henle, the distal convoluted tubule, the connecting tubule, and the intercalated cells of the collecting duct. Strikingly, in all responsive cells, parvalbumin and calbindin-D9k were exclusively present in a thin layer along the basolateral membrane. In contrast, calbindin-D28k was only present in the distal convoluted and connecting tubule, where it was evenly distributed through the cytosol. In conclusion, the exclusive localization of parvalbumin and calbindin-D9k at the basolateral membrane of immunopositive renal cells implies their involvement in the regulation of transport processes located in these membranes rather than a role as intracellular Ca2+ buffer and Ca2+ shuttle between the two opposing membranes.

Kir4.1 is specifically expressed and active in non‐myelinating Schwann cells

“…Renal expression of Kir4.1 has been extensively reported in the late thick ascending limb (TAL), the distal convoluted tubule (DCT), the connecting tubule (CNT), and the initial connecting duct (CCD; Su & Wang, 2016), and loss‐of‐function mutations in KCNJ10 lead to impaired K + homeostasis. We stained cross sections of the kidney of Kir4.1‐tdTomato mice that had been given TMX from P30‐P43 with antibodies against the cytosolic calcium‐binding protein calbindin‐D28K, which is selectively expressed in the DCT (Bindels et al, 1991). We observed extensive, but not complete, co‐labeling of tdTom+ cells (calbindin‐D28K+ cells = 68 ± 12% of tdTom+ cells; tdTom+ cells = 97.7 ± 1.2% of calbindin‐D28K+ cells; n = 3; 1 M;2F; c = 38), consistent with the wider expression pattern of Kir4.1 than calbindin‐D28K (Figure 11).…”

“…Renal expression of Kir4.1 has been extensively reported in the late thick ascending limb (TAL), the distal convoluted tubule (DCT), the connecting tubule (CNT), and the initial connecting duct (CCD; Su & Wang, 2016), and loss-of-function mutations in KCNJ10 lead to impaired K + homeostasis. We stained cross sections of the kidney of D28K, which is selectively expressed in the DCT (Bindels et al, 1991).…”

Soluble (Pro)Renin Receptor as a Negative Regulator of NCC (Na + -Cl – Cotransporter) Activity

“…For example, the specificity of PV-Cre-mediated gene recombination is limited. Despite the strict restriction of high PV abundance to the DCT1 in the mouse kidneys, 32,59 the expression is also detected in extrarenal tissues such as the neurons. Indeed, we observed modest recombination event in the brain, which may have some confounding influence on the renal phenotype.…”

Enriched Single-Nucleus RNA-Sequencing Reveals Unique Attributes of Distal Convoluted Tubule Cells

“…[25][26][27][28][29][30][31][32][33] Ca score was computed from the average expression of a curated list of known calciotropic genes expressed in the DCT that have reported calcium derangement phenotype, namely Trpv5, Calb1, Slc8a1, S100g, Vdr, and Ryr2. [34][35][36][37][38][39][40] Data Visualization Dimension, feature, dot, and violin plots were generated from built-in Seurat visualization functions. Score density plots were generated using the density function of ggplot2.…”

“…To better characterize the expression patterns for genes involved in divalent ion metabolism, we defined a magnesium cassette, with genes relevant to magnesium transport (Trpm6, Trpm7, Egf, Umod, Prox1, Fxyd2, Cnnm2, and Slc41a3), [25][26][27][28][29][30][31][32][33] and a calcium cassette, with genes relevant to calcium transport (Slc8a1, Calb1, Vdr, S100g, Trpv5, and Ryr2). [34][35][36][37][38][39][40] As we did with the DCT1 and DCT2 scores, we amalgamated the magnesium/calcium cassette gene expression into magnesium and calcium scores. As expected, the magnesium cassette is enriched in DCT1 cells, whereas the calcium cassette is enriched in DCT2 cells (Figure 3, F and G).…”