High-level expression of Dok-1 in neurons of the primate prefrontal cortex and hippocampus

Dok adaptors play anti-inflammatory roles in pulmonary homeostasis

Asthma is a chronic inflammatory disease of the lung with airflow obstruction and bronchospasm, characterized by pulmonary eosinophilia, airway remodeling, increased airway hyperresponsiveness to environmental stimuli, and excessive Th2-type cytokine production. Recent studies indicate that crosstalk between the innate and adaptive immune systems is crucial for this disease. We and others have showed that the Dok (downstream of tyrosine kinases) family adaptors, Dok-1, Dok-2, and Dok-3, play essential roles in negative regulation of a wide variety of signaling pathways in both innate and adaptive immunities. Here, histopathology and bronchoalveolar lavage fluid (BALF) cellularity showed spontaneous pulmonary inflammation in Dok-1-/- Dok-2-/- Dok-3-/- (TKO) mice, but not in Dok-1-/- Dok-2-/- or Dok-3-/- mice, with hallmarks of asthma, including eosinophilia, goblet cell hyperplasia, and subepithelial fibrosis. Consistently, TKO mice, but not the other mutants, showed increased airway hyperresponsiveness to methacholine inhalation. In addition, Th2-type cytokine concentrations in BALF were increased in TKO mice. These findings provide strong evidence that Dok-1, Dok-2, and Dok-3 cooperatively play critical anti-inflammatory roles in lung homeostasis.

The roles of Dok family adapters in immunoreceptor signaling

The mammalian Dok protein family has seven members (Dok-1-Dok-7). The Dok proteins share structural similarities characterized by the NH2-terminal pleckstrin homology and phosphotyrosine-binding domains followed by SH2 target motifs in the COOH-terminal moiety, indicating an adapter function. Indeed, Dok-1 was originally identified as a 62 kDa protein that binds with p120 rasGAP, a potent inhibitor of Ras, upon tyrosine phosphorylation by a variety of protein tyrosine kinases. Among the Dok family, only Dok-1, Dok-2, and Dok-3 are preferentially expressed in hematopoietic/immune cells. Dok-1 and its closest relative Dok-2 act as negative regulators of the Ras-Erk pathway downstream of many immunoreceptor-mediated signaling systems, and it is believed that recruitment of p120 rasGAP by Dok-1 and Dok-2 is critical to their negative regulation. By contrast, Dok-3 does not bind with p120 rasGAP. However, accumulating evidence has demonstrated that Dok-3 is a negative regulator of the activation of JNK and mobilization of Ca2+ in B-cell receptor-mediated signaling, where the interaction of Dok-3 with SHIP-1 and Grb2 appears to be important. Here, we review the physiological roles and underlying mechanisms of Dok family proteins.

The effect of sevoflurane anesthesia on cognitive function and the expression of Insulin-like Growth Factor-1 in CA1 region of hippocampus in old rats

To investigate the effects of sevoflurane on cognitive function in old Sprague-Dawley (SD) rats and the expression of insulin-like growth factor-1 (IGF-1) in CA1 region of hippocampus. Forty Sprague-Dawley rats of 12 months old were randomly divided into five groups: the normal control group; 1.5% sevoflurane I group (be tested after received 1.5% sevoflurane for 1 day); 1.5% sevoflurane II group (be tested after received 1.5% sevoflurane for 7 day); 3.0% sevoflurane I group (be tested after received 3.0% sevoflurane for 1 day) and 3.0% sevoflurane II group (be tested after received 3.0% sevoflurane for 7 day). All SD rats were received 1.5 or 3.0% sevoflurane in a special glass anesthesia box for 2 h respectively, except for the normal control group. Y-maze was used to test the ability of learning and memory after being received sevoflurane for 1 or 7 days at the same moment portion. The altered expression level of IGF-1 in the hippocampus was tested to compare its transcripts by RT-PCR analysis. The results showed that 3% sevoflurane induced the decline of cognitive function and significantly deceased the IGF-1 expression at mRNA levels at 1 day in the 3.0% sevoflurane I group when compared with the normal control group. However, there were no significant difference among the other groups when compared with normal control group. Therefore, administration of sevoflurane might temporally affect the ability of cognitive function of rats through suppressing the IGF-1 expression at mRNA levels in hippocampus.

The insulin-like growth factor (IGF) receptor type 1 (IGF1R) as an essential component of the signalling network regulating neurogenesis

The insulin-like growth factor receptor type 1 (IGF1R) signalling pathway is activated in the mammalian nervous system from early developmental stages. Its major effect on developing neural cells is to promote their growth and survival. This pathway can integrate its action with signalling pathways of growth and morphogenetic factors that induce cell fate specification and selective expansion of specified neural cell subsets. This suggests that during developmental and adult neurogenesis cellular responses to many signalling factors, including ligands of Notch, sonic hedgehog, fibroblast growth factor family members, ligands of the epidermal growth factor receptor, bone morphogenetic proteins and Wingless and Int-1, may be modified by co-activation of the IGF1R. Modulation of cell migration is another possible role that IGF1R activation may play in neurogenesis. Here, I briefly overview neurogenesis and discuss a role for IGF1R-mediated signalling in the developing and mature nervous system with emphasis on crosstalk between the signalling pathways of the IGF1R and other factors regulating neural cell development and migration. Studies on neural as well as on non-neural cells are highlighted because it may be interesting to test in neurogenic paradigms some of the models based on the information obtained in studies on non-neural cell types.

The insulin-like growth factor system and its pleiotropic functions in brain

In recent years, much interest has been devoted to defining the role of the IGF system in the nervous system. The ubiquitous IGFs, their cell membrane receptors, and their carrier binding proteins, the IGFBPs, are expressed early in the development of the nervous system and are therefore considered to play a key role in these processes. In vitro studies have demonstrated that the IGF system promotes differentiation and proliferation and sustains survival, preventing apoptosis of neuronal and brain derived cells. Furthermore, studies of transgenic mice overexpressing components of the IGF system or mice with disruptions of the same genes have clearly shown that the IGF system plays a key role in vivo.

The control of responsiveness in ADHD by catecholamines: evidence for dopaminergic, noradrenergic and interactive roles

We explore the neurobiological bases of attention deficit hyperactivity disorder (ADHD) from the viewpoint of the neurochemistry and psychopharmacology of the catecholamine-based behavioural systems. The contributions of dopamine (DA) and noradrenaline (NA) neurotransmission to the motor and cognitive symptoms of ADHD (e.g. hyperactivity, variable and impulsive responses) are studied in rodent and primate models. These models represent elements of the behavioural units observed in subjects with ADHD clinically, or in laboratory settings (e.g. locomotion, changed sensitivity/responsivity to novelty/reinforcement and measures of executive processing). In particular, the models selected emphasize traits that are strongly influenced by mesocorticolimbic DA in the spontaneously hypertensive (SHR) and the Naples high excitability (NHE) rat lines. In this context, the mode of action of methylphenidate treatment is discussed. We also describe current views on the altered control by mesolimbic catecholamines of appropriate and inappropriate goal-directed behaviour, and the tolerance or intolerance of delayed reinforcement in ADHD children and animal models. Recent insights into the previously underestimated role of the NA system in the control of mesocortical DA function, and the frontal role in processing information are elaborated.

Memory performance and the growth hormone/insulin-like growth factor axis in elderly: a positron emission tomography study

The relationship between the growth hormone/insulin-like growth factor (GH-IGF)-I status and memory performance is studied in 24 elderly males and females, aged 75-85 years. Positron emission tomography (PET) was used to measure differences in regional cerebral blood flow during the performance of a delayed-non-match-to-sample (DNMTS) working memory task. Quality and speed of performance on the DNMTS task were measured separately for the easy items (3, 4 and 5 letters) and difficult items (6, 7 and 8 letters). Results were analyzed in two different groups based on the IGF-I level of the subjects (low or high IGF-I). Error rates on the working memory task were not different, but the high IGF-I group had shorter reaction times on the easy items. The high IGF-I group showed a significantly greater increase in cerebral blood flow in the left premotor cortex (easy items) and left dorsolateral prefrontal cortex (difficult items) compared to the low IGF-I group. It is concluded that elderly with high IGF-I levels are capable of faster working memory performance and increased recruitment of task-associated prefrontal regions.