ABSTRACT
Objective To investigate the effects of rotavirus ( RV) on the expression and bioactiv-ity of Na+-H+ exchanger 3 ( NHE3 ) in Caco-2 cells and the possible regulatory mechanism. Methods Caco-2 cells expressing NHE3 were constructed and divided into four groups as follows: control ( CTL ) group, RV group, BAPTA-AM ( a Ca2+ chelator) group and BAPTA-AM+RV group. Na+-H+ exchanger ac-tivity and NHE3 expression on cell surface were determined using BCECF-AM and biotinylation assay, re-spectively. Expression of Cdc42 at protein level was measured by Western blot. Results Compared with the control group, RV infection significantly decreased the activity of NHE3 and its expression on cell surface. BATPA-AM antagonized the inhibitory effects on NHE3. Moreover, the expression of Cdc42 at protein level was increased following RV infection, which was also antagonized by BATPA-AM. Conclusions Intracellu-lar Ca2+-mediated Cdc42-dependent endocytosis pathway might be involved in regulating the expression and bioactivity of NHE3 during RV infection.
ABSTRACT
Objective To observe the effects and regulatory mechanism of rotavirus infection on the expression and bioactivity of Na+/H+exchanger 3 (NHE3) on Caco-2 cells. Methods A cell model of Caco-2 cells expressing NHE3 was constructed. Four groups were set up,which were control(CTL) group, rotavirus(RV) infection group, Cdc42 inhibitor (Pirl-1) group and Pirl-1+RV group. Bioactivity and ex-pression of NHE3 on the surface of Caco-2 cells were determined by BCECF-AM and biotinylation method, respectively. Expression of Cdc42 protein was measured by Western blot. Co-immunoprecipitation was per-formed to detect the interaction between NHE3 and Cdc42. Results Compared with the CTL group,RV in-fection significantly inhibited the bioactivity and expression of NHE3 on Caco-2 cells. These inhibitory effects were antagonized by Pirl-1. Moreover,RV infection enhanced the expression of Cdc42 protein and promoted the interaction between NHE3 and Cdc42, which were also antagonized by Pirl-1. Conclusion RV infec-tion might regulate the expression and bioactivity of NHE3 through Cdc42-dependent endocytosis pathway.
ABSTRACT
Objective To observe the effect of rotavirus (RV) infection on expression level and bioactivity of Na+-H+ exchanger 3 (NHE3) in Caco-2 cells. Methods Model of NHE3-expressing Caco-2 cells was constructed and studied in terms of intervention: control, RV, clathrin antagonist chlorpromazine (CPZ), and CPZ + RV. NHE3 activity and NHE3 protein amount on cell surface were determined by BCECF-AM and biotinylation, respectively. Expression level of clathrin was assayed by Western blot. Results Compared with control group, NHE3 activity and NHE3 surface protein level significantly decreased when the cells were treated with RV. These effects could not be completely cancelled by clathrin antagonist CPZ. Moreover, RV treatment could increase cellular protein level of clathrin, which was cancelled by CPZ. Conclusions The effect of RV infection on NHE3 expression level and biological activity may be related to clathrin-dependent endocytosis pathway, and may be also affected by other endocytosis pathways.
ABSTRACT
The marked hemodynamic and hormonal changes of normal pregnancy are associated with striking alterations in renal physiology involving structure, dynamics, tubular function, and volume homeostasis. A number of acid-base or electrolyte disorders are associated with decreased or increased HCO3-reabsorption in the renal tubules. The present study was to examine the alterations of expression and distribution of Na+/HCO3-cotransporter (NBC), Na+/H+ exchanger-3 (NHE-3), and carbonic anhydrase I and II (CA I, II) proteins in the kidneys of non-pregnant (NP) and pregnant rats using Western blot analysis and immunohistochemistry. Sprague-Dawley female rats were studied on days 10 (P 10), 12 (P 12), 14 (P 14), 17 (P 17), and 19 (P 19) of pregnancy. Western blot analysis demonstrated that the expression of NBC, ~110 kDa at molecular mass, was increased in pregnant rats, particularly P 12, compared with NP rat. The expression of NHE-3, ~83 kDa at molecular mass, was increased in pregnant rats, particularly P 12 and P 14. The expression of CA I, ~30 kDa at molecular mass, was decreased in pregnant rats, particularly P 14, but, CA II protein, ~30 kDa at molecular mass, was similar NP rat. In immunohistochemistry, strong immunoreactivity of NBC of NP rat was exclusively detected in the basolateral membranes of S1 and S2 segment of proximal tubules whereas not in S3 segment. In pregnant rats, the pattern of cellular labeling of NBC was identical to that of NP rat, but signal intensity was increased, particularly P 12. In NHE-3, strong immunoreactivity was detected in apical membranes and brush borders of S3 segments and moderate in S1 and S2 segments. In pregnant rats, the pattern of cellular labeling was identical to that of NP rat, but the signal intensity was increased, particularly P 12 and P 14. Expression of CA I and II proteins was detected in entire collecting duct. Signal intensity was prominent in type A intercalated cells and moderate in type B intercalated cells. In pregnant rats, the pattern of cellular labeling of CA I and II proteins was identical to that of non-pregnant rat, but the signal intensity of CA I was decreased in cortical collecting duct, particularly P 14 and CA II was identical to that of NP rat. These results suggest that the regulation of NBC and NHE-3 expressions in the proximal tubules and CA I expression in cortical collecting duct may maintain HCO3-concentration during the pregnancy.
Subject(s)
Animals , Female , Humans , Pregnancy , Rats , Bicarbonates , Blotting, Western , Carbonic Anhydrase I , Hemodynamics , Homeostasis , Immunohistochemistry , Kidney , Membranes , Microvilli , Physiology , Rats, Sprague-Dawley , Social Control, Formal , Strikes, EmployeeABSTRACT
A number of acid-base or electrolyte disorders are associated with decreased or increased HCO3- reabsorption in the renal tubules. There has been a general agreement that potassium depletion induces and maintains metabolic alkalosis in rats. However, many researchers have approached such issue only from functional studies to investigate Na+/H+ exchanger (NHE-3) and Na+/HCO(3-) cotransporter (NBC) activity which closely relates to potassium depletion. In addition the results obtained vary according to their researchers. Thus the present study was employed Western blot analysis and immunohistochemistry together, to examine the alterations of expression and distribution of NHE-3 and NBC-1 with reference to HCO3- reabsorption in the kidneys of rats fed potassium free diets according to the periods. Western blot analysis demonstrated that NHE-3 protein, ~83 kDa at molecular mass, was abundantly expressed in normal group. All potassium-depleted groups showed significantly increased NHE-3 protein compared to normal group. NBC-1 protein, ~110 kDa at molecular mass, was moderately expressed in normal group. All potassium-depleted groups had much higher amounts of the protein than normal group. There was a highly increased amount of NBC-1 protein especially in K-depleted 1 week group. Immunohistochemistry showed positive immunoreactivity of NHE-3 in the apical membranes and brush borders of proximal renal tubule cells. Its reactivity was most prominent in the S3.S1 and S2 had moderate immunoreactivity. Potassium-depleted groups had an identical pattern of cellular labeling of NHE-3 protein compared with that of normal group. However the signal intensity of NHE-3 protein in potassium-depleted groups was much higher than that of normal group. Immunoreactivity of NBC-1 was observed exclusively in the basolateral plasma membranes of proximal tubule cells. There was a strong reactivity in the S1 and S2, whereas S3 did not show any reactivity. Potassium-deprived rats exhibited an identical pattern of cellular labeling of NBC-1 protein compared with that of normal rats. However, the signal intensity of NBC-1 protein was markedly increased in potassium-deprived rats. These results suggest that increased NHE-3 and NBC-1 expression resulted from potassium depletion in the renal proximal tubules, enhances HCO3-reabsorption and consequently maintains metabolic alkalosis.