Key Signalling Molecules (key + signalling_molecule)

Distribution by Scientific Domains

Selected Abstracts

Molecular insights into insulin action and secretion

C. J. Rhodes
Abstract Tightly co-ordinated control of both insulin action and secretion is required in order to maintain glucose homeostasis. Gene knockout experiments have helped to define key signalling molecules that affect insulin action, including insulin and insulin-like growth factor-1 (IGF-1) receptors, insulin receptor substrate (IRS) proteins and various downstream effector proteins. ,-cell function is also a tightly regulated process, with numerous factors (including certain signalling molecules) having an impact on insulin production, insulin secretion and ,-cell mass. While signalling molecules play important roles in insulin action and secretion under normal circumstances, abnormal insulin signalling in muscle, adipose tissue, liver and pancreas leads to insulin resistance and ,-cell dysfunction. In particular, the signalling protein IRS-2 may have a central role in linking these abnormalities, although other factors are likely to be involved. [source]

Differential activation of stress-responsive signalling proteins associated with altered loading in a rat skeletal muscle

Inho Choi
Abstract Skeletal muscle undergoes a significant reduction in tension upon unloading. To explore intracellular signalling mechanisms underlying this phenomenon, we investigated twitch tension, the ratio of actin/myosin filaments, and activities of key signalling molecules in rat soleus muscle during a 3-week hindlimb suspension and 2-week reloading. Twitch tension and myofilament ratio (actin/myosin) gradually decreased during unloading but progressively recovered to initial levels during reloading. To study the involvement of stress-responsive signalling proteins during these changes, the activities of protein kinase C alpha (PKC,) and three mitogen-activated protein kinases (MAPKs),c-Jun NH2 -terminal kinase (JNK), extracellular signal-regulated protein kinase (ERK), and p38 MAPK,were examined using immunoblotting and immune complex kinase assays. PKC, phosphorylation correlated positively with the tension (Pearson's r,=,0.97, P,<,0.001) and the myofilament ratio (r,=,0.83, P,<,0.01) over the entire unloading and reloading period. Treatment of the soleus muscle with a PKC activator resulted in a similar paralleled increment in both PKC, phosphorylation and the ,-sarcomeric actin expression. The three MAPKs differed in the pattern of activation in that JNK activity peaked only for the first hours of reloading, whereas ERK and p38 MAPK activities remained elevated during reloading. These results suggest that PKC, may play a pivotal role in converting loading stress to intracellular changes in contractile proteins that determine muscle tension. Differential activation of MAPKs may also help alleviate muscle damage, modulate energy transport and/or regulate the expression of contractile proteins upon altered loading. J. Cell. Biochem. © 2005 Wiley-Liss, Inc. [source]

The Arabidopsis gene SIGMA FACTOR-BINDING PROTEIN 1 plays a role in the salicylate- and jasmonate-mediated defence responses

ABSTRACT The chloroplast-localized SIB1 protein was previously identified by its interaction with SIGMA FACTOR 1 (SIG1), a component of the RNA polymerase machinery responsible for transcription of plastid genes. The physiological function of SIB1 is little known. We found that expression of SIB1 is induced by infection with Pseudomonas syringae, suggesting its possible involvement in the defence response. The sib1 loss-of-function mutation compromises induction of some defence-related genes triggered by pathogen infection and the treatments with salicylic acid (SA) and jasmonic acid (JA), two key signalling molecules in the defence response. Conversely, constitutive over-expression of SIB1 causes the plants to hyper-activate defence-related genes following pathogen infection or the SA and JA treatments, leading to enhanced resistance to infection by P. syringae. SIB1 is a member of the large plant-specific VQ motif-containing protein family, and might act as a link to connect defence signalling with chloroplast function. [source]

Low-level mechanical strain induces extracellular signal-regulated kinase 1/2 activation in alveolar epithelial cells

RESPIROLOGY, Issue 6 2008
Xiaobo HU
Background and objective: The pattern and the degree of mechanical stimuli may determine cellular responses, but little is known about how low magnitude stimuli are converted into biochemical signals in alveolar epithelial cells (AEC). The aim of this study was to explore whether extracellular signal-regulated kinases 1/2 (ERK1/2) are activated by low-level strain in A549 cells and how mechanical factors affect ERK1/2 phosphorylation. Methods: A549 cells (an AEC line) were exposed to cyclic tensile strain via a four-point bending system, with strains of different magnitude (437, 874, 1748, 3496 µstrain), duration (5, 15, 30, 60, 120 min) and frequency (0.5, 1 Hz). Phosphorylation of ERK1/2 proteins was assessed by western blot. Results: Maximal ERK1/2 phosphorylation occurred in the 874 µstrain group (a 2.25-fold increase, P < 0.01). In this group, the peak response occurred after 30 min of exposure and slowly decreased to baseline after 90 min. Static strain did not produce a statistically significant increase in ERK1/2 phosphorylation, whereas a frequency of 0.5 Hz produced a 4.56-fold increase compared with the control (P < 0.05). A 10.87-fold increase in response with frequency of 1 Hz was found. Conclusion: Low-level strain activates ERK1/2 in A549 cells. ERK1/2 may be the key signalling molecules mediating strain-induced cellular responses. [source]