Enteric Nervous System: Identification of a Novel Neuronal Sensory Network in the Duodenal Epithelium.

The communication between the intestinal epithelium and the enteric nervous system has been considered indirect. Mechanical or chemical stimuli activate enteroendocrine cells inducing hormone secretion, which act on sub-epithelial nerve ends, activating the enteric nervous system. However, we identified an epithelial cell that expresses NKAIN4, a neuronal protein associated with the β-subunit of Na/K-ATPase.

Identification and characterization of a calmodulin binding domain in the plasma membrane Ca-ATPase from Trypanosoma equiperdum.

The plasma membrane Ca-ATPase (PMCA) from trypanosomatids lacks a classical calmodulin (CaM) binding domain, although CaM stimulated activities have been detected by biochemical assays. Recently we proposed that the Trypanosoma equiperdum CaM-sensitive PMCA (TePMCA) contains a potential 1-18 CaM-binding motif at the C-terminal region of the pump. In the present study, we evaluated the potential CaM-binding motifs using CaM from Trypanosoma cruzi and either the recombinant full length TePMCA C-terminal sequence (P14) or synthetic peptides comprising different regions of the C-terminal domain.

Blood pressure, magnesium and other mineral balance in two rat models of salt-sensitive, induced hypertension: effects of a non-peptide angiotensin II receptor type 1 antagonist.

The renin-angiotensin system is critically involved in regulating arterial blood pressure (BP). Inappropriate angiotensin type-1 receptor activation by angiotensin-II (Ang-II) is related to increased arterial BP. Mg has a role in BP; it can affect cardiac electrical activity, myocardial contractility, and vascular tone.

The second sodium pump: from the function to the gene.

Transepithelial Na(+) transport is mediated by passive Na(+) entry across the luminal membrane and exit through the basolateral membrane by two active mechanisms: the Na(+)/K(+) pump and the second sodium pump. These processes are associated with the ouabain-sensitive Na(+)/K(+)-ATPase and the ouabain-insensitive, furosemide-inhibitable Na(+)-ATPase, respectively. Over the last 40 years, the second sodium pump has not been successfully associated with any particular membrane protein.

Isolation and cloning of the K+-independent, ouabain-insensitive Na+-ATPase.

Primary Na+ transport has been essentially attributed to Na+/K+ pump. However, there are functional and biochemical evidences that suggest the existence of a K+-independent, ouabain-insensitive Na+ pump, associated to a Na+-ATPase with similar characteristics, located at basolateral plasma membrane of epithelial cells. Herein, membrane protein complex associated with this Na+-ATPase was identified.

Purification and characterization of the ouabain-sensitive H+/K+-ATPase from guinea-pig distal colon.

Distal colon absorbs K+ through a Na+-independent, ouabain-sensitive H+/K+-exchange, associated to an apical ouabain-sensitive H+/K+-ATPase. Expression of HKalpha2, gene associated with this ATPase, induces K+-transport mechanisms, whose ouabain susceptibility is inconsistent. Both ouabain-sensitive and ouabain-insensitive K+-ATPase activities have been described in colonocytes.

Differential expression of P-type ATPases in intestinal epithelial cells: identification of putative new atp1a1 splice-variant.

P-type ATPases are membrane proteins that couple ATP hydrolysis with cation transport across the membrane. Ten different subtypes have been described. In mammalia, 15 genes of P-type ATPases from subtypes II-A, II-B and II-C, that transport low-atomic-weight cations (Ca(2+), Na(+), K(+) and H(+)), have been reported.

Modulation of membrane type 1 matrix metalloproteinase by LPS and gamma interferon bound to extracellular matrix in intestinal crypt cells.

Membrane type 1 matrix metalloproteinase (MT1-MMP) is an integral membrane protein that participates in the processing and degradation of cell surface proteins and the extracellular matrix (ECM). This enzyme regulates ECM turnover in wound repair, promotes cell migration and activates other MMPs, such as MMP-2, which is involved in angiogenesis, cell migration and tumoral metastasis. An increase in pro-inflammatory cytokine expression, such as gamma interferon (IFN-gamma), has been associated with chronic wounds in inflammatory bowel diseases.

Interferon gamma bound to extracellular matrix changes the hyporesponsiveness to LPS in crypt but not villous intestinal epithelial cells.

Intestinal epithelial cells (IEC) are hyporesponsive to LPS. Responsiveness to luminal bacteria has been implicated in the pathogenesis of inflammatory bowel diseases (IBD). In support of this, previous studies have demonstrated that some intestinal epithelial cell lines are induced by IFN-gamma to respond to LPS.

Backdoor phosphorylation of basolateral plasma membranes of small intestinal epithelial cells: characterization of a furosemide-induced phosphoprotein related to the second sodium pump.

Enterocyte has two different Na+-stimulated ATPases, the ouabain-sensitive Na+/K+ ATPase and a furosemide-inhibitable Na+ ATPase. To identify the polypeptide associated with the Na+-ATPase, 32Pi phosphorylation into basolateral membranes of enterocyte was investigated. Both, ouabain and furosemide induced Mg2+-dependent, vanadate-sensitive 32Pi incorporation into a 100kDa polypeptide.

Glutamine transport in isolated epithelial intestinal cells. Identification of a Na+-dependent transport mechanism, highly specific for glutamine.

L-glutamine transport was evaluated in isolated cells from the guinea-pig small intestine by measuring [(3)H]- L-glutamine uptake. Villous and crypt cells expressed Na(+)-dependent and Na(+)-independent transport mechanisms. Glutamine transport systems were identified using various amino acids and analogues as inhibitors.