Biomedical subjects

Jianghui Hou

Publications and source records attributed to Jianghui Hou.

4 recordsLinked to original sources

PubMed2006

Study of claudin function by RNA interference.

Claudins are tight junction proteins that play a key selectivity role in the paracellular conductance of ions. Numerous studies of claudin function have been carried out using the overexpression strategy to add new claudin channels to an existing paracellular protein background. Here, we report the systematic knockdown of endogenous claudin gene expression in Madin-Darby canine kidney (MDCK) cells and in LLC-PK1 cells using small interfering RNA against claudins 1-4 and 7. In MDCK cells (showing cation selectivity), claudins 2, 4, and 7 are powerful effectors of paracellular Na+ permeation. Removal of claudin-2 depressed the permeation of Na+ and resulted in the loss of cation selectivity. Loss of claudin-4 or -7 expression elevated the permeation of Na+ and enhanced the proclivity of the tight junction for cations. On the other hand, LLC-PK1 cells express little endogenous claudin-2 and show anion selectivity. In LLC-PK1 cells, claudin-4 and -7 are powerful effectors of paracellular Cl- permeation. Knockdown of claudin-4 or -7 expression depressed the permeation of Cl- and caused the tight junction to lose the anion selectivity. In conclusion, claudin-2 functions as a paracellular channel to Na+ to increase the cation selectivity of the tight junction; claudin-4 and -7 function either as paracellular barriers to Na+ or as paracellular channels to Cl-, depending upon the cellular background, to decrease the cation selectivity of the tight junction.

Animals↗

PubMed2005

Paracellin-1 and the modulation of ion selectivity of tight junctions.

Tight junctions play a key selectivity role in the paracellular conductance of ions. Paracellin-1 is a member of the tight junction claudin protein family and mutations in the paracellin-1 gene cause a human hereditary disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) with severe renal Mg2+ wasting. The mechanism of paracellin-1 function and its role in FHHNC are not known. Here, we report that in LLC-PK1 epithelial cells paracellin-1 modulated the ion selectivity of the tight junction by selectively and significantly increasing the permeability of Na+ (with no effects on Cl-) and generated a high permeability ratio of Na+ to Cl-. Mutagenesis studies identified a locus of amino acids in paracellin-1 critical for this function. Mg2+ flux across cell monolayers showed a far less-pronounced change (compared to monovalent alkali cations) following exogenous protein expression, suggesting that paracellin-1 did not form Mg2+-selective paracellular channels. We hypothesize that in the thick ascending limb of the nephron, paracellin-1 dysfunction, with a concomitant loss of cation selectivity, could contribute to the dissipation of the lumen-positive potential that is the driving force for the reabsorption of Mg2+.

Amino Acid Sequence↗

PubMed2002

Design of endonuclease restriction sites into primers for PCR cloning.

I present a software system PCRCLNG that facilitates the design of endonuclease restriction sites into the 5'-end of PCR primers. The product amplified using these primers can be directly cloned into vectors. The program estimates the annealing temperature for each primer and selects the primer pairs with comparable annealing temperature. Finally the software determines whether the PCR product can be cloned into the vector to generate in-frame gene fusion.

Algorithms↗

PubMed2002

Sgk1 gene expression in kidney and its regulation by aldosterone: spatio-temporal heterogeneity and quantitative analysis.

The serine-threonine kinase sgk1 was recently identified as a gene rapidly induced by mineralocorticoids, resulting in increased sodium transport in vitro. To carefully localize and quantify the renal sgk1 expression response to aldosterone, in situ hybridization was performed on kidneys of mice having aldosterone excess over a range of doses and durations. In control and adrenalectomized animals, the glomeruli and inner medullary collecting ducts were the major sites of sgk1 expression, which was maintained independent of aldosterone. Sgk1 upregulation induced by aldosterone excess exhibited spatio-temporal heterogeneity. Both acute (3-h) and chronic (6-d) aldosterone excess stimulated sgk1 expression in the distal nephron, i.e., from the distal convoluted tubules through to the outer medullary collecting ducts. Treatments for 6 d with low sodium diet (0.03% [I]) and aldosterone infusions (50 microg/kg per d [II], 150 microg/kg per d [III], and 750 microg/kg per d [IV]) generated elevation of circulating aldosterone. Across these treatments (I through IV), the circulating level correlated with the progressive induction of sgk1 expression, with highly stimulated tubules first appearing in cortex (I) and continuing downward (II) until there was a strong stimulation throughout outer medulla (III and IV). Interestingly, chronic but not acute aldosterone excess caused a slight increase of sgk1 expression in glomerulus (30 to 50%; P < 0.01) and a dramatic downregulation in the initial portion of inner medulla, which could result from diminished interstitial osmolarity. Relative quantification (versus control) of sgk1 upregulation in individual tubules revealed: (1) a 1.8-fold increase of sgk1 mRNA at 3 h (150 microg/kg injection) and (2) a dose-dependence of chronic upregulation reaching a ceiling of eightfold elevation.

Aldosterone↗