scholarly journals Exon Loss Accounts for Differential Sorting of Na-K-Cl Cotransporters in Polarized Epithelial Cells

2008 ◽  
Vol 19 (10) ◽  
pp. 4341-4351 ◽  
Author(s):  
Monica Carmosino ◽  
Ignacio Giménez ◽  
Michael Caplan ◽  
Biff Forbush

The renal Na-K-Cl cotransporter (NKCC2) is selectively expressed in the apical membranes of cells of the mammalian kidney, where it is the target of the clinically important loop diuretics. In contrast, the “secretory” NKCC1 cotransporter is localized in the basolateral membranes of many epithelia. To identify the sorting signal(s) that direct trafficking of NKCCs, we generated chimeras between the two isoforms and expressed these constructs in polarized renal epithelial cell lines. This analysis revealed an amino acid stretch in NKCC2 containing apical sorting information. The NKCC1 C terminus contains a dileucine motif that constitutes the smallest essential component of its basolateral sorting signal. NKCC1 lacking this motif behaves as an apical protein. Examination of the NKCC gene structure reveals that this dileucine motif is encoded by an additional exon in NKCC1 absent in NKCC2. Phylogenetic analysis of this exon suggests that the evolutionary loss of this exon from the gene encoding the basolateral NKCC1 constitutes a novel mechanism that accounts for the apical sorting of the protein encoded by the NKCC2 gene.

2012 ◽  
Vol 11 (8) ◽  
pp. 1055-1066 ◽  
Author(s):  
Matthias Kretschmer ◽  
Jana Klose ◽  
James W. Kronstad

ABSTRACTAn understanding of metabolic adaptation during the colonization of plants by phytopathogenic fungi is critical for developing strategies to protect crops. Lipids are abundant in plant tissues, and fungal phytopathogens in the phylum basidiomycota possess both peroxisomal and mitochondrial β-oxidation pathways to utilize this potential carbon source. Previously, we demonstrated a role for the peroxisomal β-oxidation enzyme Mfe2 in the filamentous growth, virulence, and sporulation of the maize pathogenUstilago maydis. However,mfe2mutants still caused disease symptoms, thus prompting a more detailed investigation of β-oxidation. We now demonstrate that a defect in thehad1gene encoding hydroxyacyl coenzyme A dehydrogenase for mitochondrial β-oxidation also influences virulence, although its paralog,had2, makes only a minor contribution. Additionally, we identified a gene encoding a polypeptide with similarity to the C terminus of Mfe2 and designated it Mfe2b; this gene makes a contribution to virulence only in the background of anmfe2Δ mutant. We also show that short-chain fatty acids induce cell death inU. maydisand that a block in β-oxidation leads to toxicity, likely because of the accumulation of toxic intermediates. Overall, this study reveals that β-oxidation has a complex influence on the formation of disease symptoms byU. maydisthat includes potential metabolic contributions to proliferationin plantaand an effect on virulence-related morphogenesis.


1984 ◽  
Vol 66 (1) ◽  
pp. 81-93
Author(s):  
F.V. Sepulveda ◽  
J.D. Pearson

We have studied the cell-to-cell passage of uridine nucleotides in two renal epithelial cell lines (LLC-PK1 and MDCK) and in porcine aortic endothelial cells (PAE). All three cell types incorporated tritiated uridine. After a 3 h incubation the radioactivity was predominantly in the form of acid-soluble compounds, mainly UTP. Prelabelled LLC-PK1 or MDCK cells were unable to transfer radioactivity to added adjacent, non-labelled cells, whereas PAE cells readily formed communicating intercellular junctions, as judged by autoradiographic analysis after a 3 h co-culture period. Cell-to-cell communication in either of the renal cell lines was not promoted by treatment with dibutyryl cyclic AMP and methylisobutylxanthine. Radioactivity incorporated into the acid-insoluble pool was not available for intercellular transfer, as assessed in experiments in which cells were prelabelled 24 h before co-culture.


eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Laura Dean Heckman ◽  
Maria H Chahrour ◽  
Huda Y Zoghbi

Loss of function of the X-linked gene encoding methyl-CpG binding protein 2 (MeCP2) causes the progressive neurological disorder Rett syndrome (RTT). Conversely, duplication or triplication of Xq28 causes an equally wide-ranging progressive neurological disorder, MECP2 duplication syndrome, whose features overlap somewhat with RTT. To understand which MeCP2 functions cause toxicity in the duplication syndrome, we generated mouse models expressing endogenous Mecp2 along with a RTT-causing mutation in either the methyl-CpG binding domain (MBD) or the transcriptional repression domain (TRD). We determined that both the MBD and TRD must function for doubling MeCP2 to be toxic. Mutating the MBD reproduces the null phenotype and expressing the TRD mutant produces milder RTT phenotypes, yet both mutations are harmless when expressed with endogenous Mecp2. Surprisingly, mutating the TRD is more detrimental than deleting the entire C-terminus, indicating a dominant-negative effect on MeCP2 function, likely due to the disruption of a basic cluster.


1989 ◽  
Vol 1010 (3) ◽  
pp. 311-317 ◽  
Author(s):  
Christoph Korbmacher ◽  
Wolfgang Schulz ◽  
Michael König ◽  
Harald Siebe ◽  
Ingrid Lichtenstein ◽  
...  

1997 ◽  
Vol 94 (23) ◽  
pp. 12285-12290 ◽  
Author(s):  
A. M. Gabilondo ◽  
J. Hegler ◽  
C. Krasel ◽  
V. Boivin-Jahns ◽  
L. Hein ◽  
...  

1993 ◽  
Vol 265 (1) ◽  
pp. F137-F145 ◽  
Author(s):  
D. P. Jones ◽  
L. A. Miller ◽  
R. W. Chesney

We characterized taurine transport in two continuous renal epithelial cell lines: LLC-PK1, derived from the proximal tubule of the pig, and the Madin-Darby canine kidney (MDCK), which was originated from the distal tubule of the dog. In the LLC-PK1 cell line, taurine transport is greatest at the apical surface of the cell, whereas in the MDCK cell line taurine transport is greatest at the basolateral surface. Both apical and basolateral surfaces of LLC-PK1 and MDCK cells exhibit an adaptive response to the extracellular taurine concentration (medium taurine concentration). Only the basolateral surface of the MDCK cell responded to hyperosmolality with increased taurine accumulation. This indicates differential control of the beta-amino acid transport system by substrate and external tonicity. The function of the beta-amino acid transport system may be different depending on the cell. In the LLC-PK1 cell, there is net transepithelial movement of taurine and changes in transporter activity in response to supply of substrate. In contrast, taurine accumulation by the MDCK cell appears to be a mechanism for adaptation to osmotic stress.


2000 ◽  
Vol 182 (23) ◽  
pp. 6857-6861 ◽  
Author(s):  
Beatriz Martı́nez ◽  
Jouko Sillanpää ◽  
Egbert Smit ◽  
Timo K. Korhonen ◽  
Peter H. Pouwels

The cbsA gene encoding the collagen-binding S-layer protein of Lactobacillus crispatus JCM5810 was expressed inL. casei ATCC 393T. The S-protein was not retained on the surface of the recombinant bacteria but was secreted into the medium. By translational fusion of CbsA to the cell wall sorting signal of the proteinase, PrtP, of L. casei, CbsA was presented at the surface, rendering the transformants able to bind to immobilized collagens.


FEBS Letters ◽  
1992 ◽  
Vol 308 (1) ◽  
pp. 14-17 ◽  
Author(s):  
Lotte Katrine Vogel ◽  
Ove Norén ◽  
Hans Sjöström

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