| 1. |
- Al-Khalili, L, et al.
(författare)
-
Proteasome inhibition in skeletal muscle cells unmasks metabolic derangements in type 2 diabetes
- 2014
-
Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 307:9, s. C774-C787
-
Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional difference gel electrophoresis (2-D DIGE)-based proteome analysis has revealed intrinsic insulin resistance in myotubes derived from type 2 diabetic patients. Using 2-D DIGE-based proteome analysis, we identified a subset of insulin-resistant proteins involved in protein turnover in skeletal muscle of type 2 diabetic patients, suggesting aberrant regulation of the protein homeostasis maintenance system underlying metabolic disease. We then validated the role of the ubiquitin-proteasome system (UPS) in myotubes to investigate whether impaired proteasome function may lead to metabolic arrest or insulin resistance. Myotubes derived from muscle biopsies obtained from people with normal glucose tolerance (NGT) or type 2 diabetes were exposed to the proteasome inhibitor bortezomib (BZ; Velcade) without or with insulin. BZ exposure increased protein carbonylation and lactate production yet impaired protein synthesis and UPS function in myotubes from type 2 diabetic patients, marking the existence of an insulin-resistant signature that was retained in cultured myotubes. In conclusion, BZ treatment further exacerbates insulin resistance and unmasks intrinsic features of metabolic disease in myotubes derived from type 2 diabetic patients. Our results highlight the existence of a confounding inherent abnormality in cellular protein dynamics in metabolic disease, which is uncovered through concurrent inhibition of the proteasome system.
|
|
| 2. |
- Dahan, Diana, et al.
(författare)
-
Induction of angiotensin converting enzyme after miR-143/145 deletion is critical for impaired smooth muscle contractility.
- 2014
-
Ingår i: American Journal of Physiology: Cell Physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 307:12, s. 1093-1101
-
Tidskriftsartikel (refereegranskat)abstract
- MicroRNAs have emerged as regulators of smooth muscle cell phenotype with a role in smooth muscle-related disease. Studies have shown that miR-143 and miR-145 are the most highly expressed microRNAs in smooth muscle cells, controlling differentiation and function. The effect of miR-143/145 knockout has been established in the vasculature but not in smooth muscle from other organs. Using knockout mice we found that maximal contraction induced by either depolarization or phosphatase inhibition was reduced in vascular and airway smooth muscle but maintained in the urinary bladder. Furthermore, a reduction of media thickness and reduced expression of differentiation markers was seen in the aorta but not in the bladder. Supporting the view that phenotype switching depends on a tissue-specific target of miR-143/145, we found induction of angiotensin converting enzyme in the aorta but not in the bladder where angiotensin converting enzyme was expressed at a low level. Chronic treatment with angiotensin type-1 receptor antagonist restored contractility in miR-143/145-deficient aorta while leaving bladder contractility unaffected. This shows that tissue-specific targets are critical for the effects of miR-143/145 on smooth muscle differentiation and that angiotensin converting enzyme is one such target.
|
|
| 3. |
- Defourny, J, et al.
(författare)
-
Structure and development of cochlear afferent innervation in mammals
- 2011
-
Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 301:4, s. C750-C761
-
Tidskriftsartikel (refereegranskat)abstract
- In mammals, sensorineural deafness results from damage to the auditory receptors of the inner ear, the nerve pathways to the brain or the cortical area that receives sound information. In this review, we first focused on the cellular and molecular events taking part to spiral ganglion axon growth, extension to the organ of Corti, and refinement. In the second half, we considered the functional maturation of synaptic contacts between sensory hair cells and their afferent projections. A better understanding of all these processes could open insights into novel therapeutic strategies aimed to re-establish primary connections from sound transducers to the ascending auditory nerve pathways.
|
|
| 4. |
|
|
| 5. |
- Kappe, C, et al.
(författare)
-
Evidence for paracrine/autocrine regulation of GLP-1-producing cells
- 2013
-
Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 305:10, s. C1041-C1049
-
Tidskriftsartikel (refereegranskat)abstract
- Glucagon-like peptide-1 (GLP-1), secreted from gut L cells upon nutrient intake, forms the basis for novel drugs against type 2 diabetes (T2D). Secretion of GLP-1 has been suggested to be impaired in T2D and in conditions associated with hyperlipidemia and insulin resistance. Further, recent studies support lipotoxicity of GLP-1-producing cells in vitro. However, little is known about the regulation of L-cell viability/function, the effects of insulin signaling, or the potential effects of stable GLP-1 analogs and dipeptidyl peptidase-4 (DPP-4) inhibitors. We determined effects of insulin as well as possible autocrine action of GLP-1 on viability/apoptosis of GLP-1-secreting cells in the presence/absence of palmitate, while also assessing direct effects on function. The studies were performed using the GLP-1-secreting cell line GLUTag, and palmitate was used to simulate hyperlipidemia. Our results show that palmitate induced production of reactive oxygen species and caspase-3 activity and reduced cell viability are significantly attenuated by preincubation with insulin/exendin-4. The indicated lipoprotective effect of insulin/exendin-4 was not detectable in the presence of the GLP-1 receptor (GLP-1R) antagonist exendin (9–39) and attenuated in response to pharmacological inhibition of exchange protein activated by cAMP (Epac) signaling, while protein kinase A inhibition had no significant effect. Insulin/exendin-4 also significantly stimulate acute and long-term GLP-1 secretion in the presence of glucose, suggesting novel beneficial effects of insulin signaling and GLP-1R activation on glycemia through enhanced mass of GLP-1-producing cells and enhanced GLP-1 secretion. In addition, the effects of insulin indicate that not only is GLP-1 important for insulin secretion but altered insulin signaling may contribute to an altered GLP-1 secretion.
|
|
| 6. |
- Liu, Chang, et al.
(författare)
-
NHE8 plays an important role in mucosal protection via its effect on bacterial adhesion.
- 2013
-
Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 305:1
-
Tidskriftsartikel (refereegranskat)abstract
- The Na(+)/H(+) exchanger NHE8 is expressed on the apical membrane of intestinal epithelial cells and is particularly abundant in the colon. Our previous study showed that Muc2 expression was significantly reduced in NHE8-knockout (NHE8(-/-)) mice, suggesting that NHE8 plays a role in mucosal protection in the colon. The current study confirms and extends our studies on the role of NHE8 in mucosal protection. The number of bacteria attached on the distal colon was significantly increased in NHE8(-/-) mice compared with their wild-type littermates. As expected, IL-4 expression was markedly increased in NHE8(-/-) mice compared with wild-type mice. Immunohistochemistry showed disorganization in the mucin layer of NHE8(-/-) mice, suggesting a possible direct bacteria-epithelia interaction. Furthermore, NHE8(-/-) mice were susceptible to dextran sodium sulfate-induced mucosal injury. In wild-type mice, dextran sodium sulfate treatment inhibited colonic NHE8 expression. In Caco-2 cells, the absence of NHE8 expression resulted in higher adhesion rates of Salmonella typhimurium but not Lactobacillus plantarum. Similarly, in vivo, S. typhimurium adhesion rate was increased in NHE8(-/-) mice compared with wild-type mice. Our study suggests that NHE8 plays important roles in protecting intestinal epithelia from infectious bacterial adherence.
|
|
| 7. |
- Pelaseyed, Thaher, 1979, et al.
(författare)
-
Carbachol-induced MUC17 endocytosis is concomitant with NHE3 internalization and CFTR membrane recruitment in enterocytes.
- 2013
-
Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 305:4
-
Tidskriftsartikel (refereegranskat)abstract
- We have reported that transmembrane mucin MUC17 binds PDZ protein PDZK1, which retains MUC17 apically in enterocytes. MUC17 and transmembrane mucins MUC3 and MUC12 are suggested to build the enterocyte apical glycocalyx. Carbachol (CCh) stimulation of the small intestine results in gel-forming mucin secretion from goblet cells, something that requires adjacent enterocytes to secrete chloride and bicarbonate for proper mucin formation. Surface labeling and confocal imaging demonstrated that apically expressed MUC17 in Caco-2 cells and Muc3(17) in murine enterocytes were endocytosed upon stimulation with CCh. Relocation of MUC17 in response to CCh was specific as MUC3 and MUC12 did not relocate following CCh stimulation. MUC17 colocalized with PDZK1 under basal conditions, while MUC17 relocated to the terminal web and into early endosomes after CCh stimulation. CCh stimulation concomitantly internalized the Na(+/)H(+) exchanger 3 (NHE3) and recruited cystic fibrosis transmembrane conductance regulator (CFTR) to the apical membranes, a process that was important for CFTR-mediated bicarbonate secretion necessary for proper gel-forming mucin unfolding. The reason for the specific internalization of MUC17 is not understood, but it could limit the diffusion barrier for ion secretion caused by the apical enterocyte glycocalyx or alternatively act to sample luminal bacteria. Our results reveal well-orchestrated mucus secretion and trafficking of ion channels and the MUC17 mucin.
|
|
| 8. |
- Pirkmajer, S, et al.
(författare)
-
Serum starvation: caveat emptor
- 2011
-
Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 301:2, s. C272-C279
-
Tidskriftsartikel (refereegranskat)abstract
- Serum starvation is one of the most frequently performed procedures in molecular biology and there are literally thousands of research papers reporting its use. In fact, this method has become so ingrained in certain areas of research that reports often simply state that cells were serum starved without providing any factual details as to how the procedure was carried out. Even so, we quite obviously lack unequivocal terminology, standard protocols, and perhaps most surprisingly, a common conceptual basis when performing serum starvation. Such inconsistencies not only hinder interstudy comparability but can lead to opposing and inconsistent experimental results. Although it is frequently assumed that serum starvation reduces basal activity of cells, available experimental data do not entirely support this notion. To address this important issue, we studied primary human myotubes, rat L6 myotubes and human embryonic kidney (HEK)293 cells under different serum starvation conditions and followed time-dependent changes in important signaling pathways such as the extracellular signal-regulated kinase 1/2, the AMP-activated protein kinase, and the mammalian target of rapamycin. Serum starvation induced a swift and dynamic response, which displayed obvious qualitative and quantitative differences across different cell types and experimental conditions despite certain unifying features. There was no uniform reduction in basal signaling activity. Serum starvation clearly represents a major event that triggers a plethora of divergent responses and has therefore great potential to interfere with the experimental results and affect subsequent conclusions.
|
|
| 9. |
- Singh, Anurag Kumar, et al.
(författare)
-
The switch of intestinal Slc26 exchangers from anion absorptive to HCO3- secretory mode is dependent on CFTR anion channel function
- 2010
-
Ingår i: American Journal of Physiology - Cell Physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 298:5, s. C1057-C1065
-
Tidskriftsartikel (refereegranskat)abstract
- Singh AK, Riederer B, Chen M, Xiao F, Krabbenhoft A, Engelhardt R, Nylander O, Soleimani M, Seidler U. The switch of intestinal Slc26 exchangers from anion absorptive to HCO3- secretory mode is dependent on CFTR anion channel function. Am J Physiol Cell Physiol 298: C1057-C1065, 2010. First published February 17, 2010; doi:10.1152/ajpcell.00454.2009.-CFTR has been recognized to function as both an anion channel and a key regulator of Slc26 anion transporters in heterologous expression systems. Whether this regulatory relationship between CFTR and Slc26 transporters is seen in native intestine, and whether this effect is coupled to CFTR transport function or other features of this protein, has not been studied. The duodena of anesthetized CFTR-, NHE3-, Slc26a6-, and Scl26a3-deficient mice and wild-type (WT) littermates were perfused, and duodenal bicarbonate (HCO3-) secretion (DBS) and fluid absorptive or secretory rates were measured. The selective NHE3 inhibitor S1611 or genetic ablation of NHE3 significantly reduced fluid absorptive rates and increased DBS. Slc26a6 (PAT1) or Slc26a3 (DRA) ablation reduced the S1611-induced DBS increase and reduced fluid absorptive rates, suggesting that the effect of S1611 or NHE3 ablation on HCO3- secretion may be an unmasking of Slc26a6- and Slc26a3-mediated Cl-/HCO3- exchange activity. In the absence of CFTR expression or after application of the CFTR(inh)-172, fluid absorptive rates were similar to those of WT, but S1611 induced virtually no increase in DBS, demonstrating that CFTR transport activity, and not just its presence, is required for Slc26-mediated duodenal HCO3- secretion. A functionally active CFTR is an absolute requirement for Slc26-mediated duodenal HCO3- secretion, but not for Slc26-mediated fluid absorption, in which these transporters operate in conjunction with the Na+/H+ exchanger NHE3. This suggests that Slc26a6 and Slc26a3 need proton recycling via NHE3 to operate in the Cl- absorptive mode and Cl- exit via CFTR to operate in the HCO3- secretory mode.
|
|
| 10. |
|
|
