What is the kinase that phosphorylates mGluR5 and how is its activity coordinated with this signaling pathway? To what degree does tyrosine phosphorylation change signaling output from mGluR5? What are the essential sites for rules of mGluR5 function? HIGHLIGHTS Part for PTP1B in endocannabinoid signaling Novel therapeutic strategy for anxiety disorders PTP1B while anxiolytics ACKNOWLEDGMENTS Work in the authors lab is supported by by NIH grants CA53840 and GM55989, and the CSHL Malignancy Centre Support Give CA45508

What is the kinase that phosphorylates mGluR5 and how is its activity coordinated with this signaling pathway? To what degree does tyrosine phosphorylation change signaling output from mGluR5? What are the essential sites for rules of mGluR5 function? HIGHLIGHTS Part for PTP1B in endocannabinoid signaling Novel therapeutic strategy for anxiety disorders PTP1B while anxiolytics ACKNOWLEDGMENTS Work in the authors lab is supported by by NIH grants CA53840 and GM55989, and the CSHL Malignancy Centre Support Give CA45508. and may itself be a substrate of PTP1B, but again the degree to which this occurs and its significance under physiological conditions is definitely unclear. Finally, in assessing the effects of LMO4 on the activity of PTP1B, GF 109203X the authors use a PhosphoSeek PTP1B Assay Kit from BioVision. This kit is designed as an assay for screening activity of the purified protein in vitro and does not consist of any step for enriching PTP1B from cell lysates. As a result, the activity that is being measured with this study will be that of any PTP in the cell lysate that recognizes the fluorescent dye substrate, which is likely to reflect several PTPs and not just PTP1B only. Consequently, although there are attractive features to this part of the model, a more quantitative approach to define precisely the stoichiometries of association and to investigate further the significance of oxidation of PTP1B for the effects of LMO4 will be required to test its validity. The importance of tyrosine phosphorylation for rules of mGluR5 function Another central feature of the model is the rules of mGluR5 by reversible tyrosine phosphorylation; however, the regulatory importance of such phosphorylation remains to be defined. Glutamate receptors, such as mGluR5, are G protein-coupled receptors that are linked to activation of phospholipase C and phosphatidylinositol phospholipid turnover, with the launch of GF 109203X Ca2+ from intracellular stores and the modulation of multiple downstream signaling pathways, in particular those involved in protein translation [6]. Studies of mGluR5 tyrosine phosphorylation have focused on screening the effects of broad specificity kinase and phosphatase inhibitors [7]. It has been reported that mGluR5 is definitely tyrosine phosphorylated, but only after treatment with the broad specificity PTP inhibitor pervanadate [7]. Furthermore, this phosphorylation was not associated with any changes in phosphatidylinositol phospholipid turnover, so the significance with respect to rules of signaling remains unclear [8]. In this study, the authors demonstrate tyrosine phosphorylation of mGluR5, but further work is needed to define the stoichiometry of phosphorylation, to identify the sites that are phosphorylated, to identify the PTK responsible for the phosphorylation and to validate that this modification is definitely linked to a change in signaling. It will be of interest also to examine where in the cell such phosphorylation may occur. It has been reported that different subcellular swimming pools of mGluR5 may be associated with different signaling results [8]. Considering the ER localization of PTP1B [1] and recent reports that there are intracellular swimming pools of mGluR5, including in the ER, it will be interesting to test whether PTP1B exerts effects on receptors in the cell surface or on intracellular membranes. Stress, endocannabinoid signaling and panic The authors mentioned the phenotype of the LMO4-knockout mouse resembles that seen following chronic stress or loss of eCB signaling. Consequently, they required the complementary approach of testing the effects of chronic stress stimuli within the proposed GF 109203X signaling cascade and the development of panic. They subjected mice to a daily routine of restraint stress over a period of eight days, which resulted in increased levels of the GF 109203X stress hormone corticosterone in the blood. The authors statement that these effects coincided with elevated CDC42 PTP1B activity in the amygdala, and in neuronal cells exposed to corticosterone in tradition, due to a decrease in the amount of the oxidized inactive form of the phosphatase, which coincided with attenuation of stress-induced decrease in eCBs. Furthermore, they statement that treatment with the glucocorticoid receptor antagonist RU486 during chronic stress normalized PTP1B activity in the amygdala. However, one caveat of these studies with respect to the proposal that the effects of LMO4 on PTP1B activity was mediated through changes in redox rules of the phosphatase is that chronic stress, such as the restraint stress regimen used here, has been reported to lead also to enhanced oxidative stress. In fact, such acute restraint stress has been reported to induce manifestation of NADPH oxidases, which are major enzymes that promote PTP oxidation and inactivation in cells [9]. Considering the susceptibility to oxidation and inactivation of the catalytic cysteine residue in the PTP active site, one might have anticipated that restraint stress would lead to enhanced oxidation and inactivation of those PTPs that colocalize with the NADPH oxidases. In addition, it remains unclear from your protocol used in this study, which PTPs are becoming measured in the activity assay and the degree to which PTP1B contributes to the activity that was recognized. Further studies will be required to determine more precisely the mechanism by which PTP1B activity may be regulated with this context. Trodusquemine/MSI-1436 C an allosteric inhibitor of PTP1B and drug candidate Although it has been possible to generate potent, specific and reversible small molecule inhibitors of PTP1B, the.