For more than 60 years, the mood stabilizer lithium has been used alone or in combination for the treatment of bipolar disorder, schizophrenia, depression, and other mental illnesses. Despite this long history, the molecular mechanisms trough which lithium regulates behavior are still poorly understood. Among several targets, lithium has been shown to directly inhibit glycogen synthase kinase 3 alpha and beta (GSK3α and GSK3β). However in vivo, lithium also inhibits GSK3 by regulating other mechanisms like the formation of a signaling complex comprised of beta-arrestin 2 (βArr2) and Akt. Here, we provide an overview of in vivo evidence supporting a role for inhibition of GSK3 in some behavioral effects of lithium. We also explore how regulation of GSK3 by lithium within a signaling network involving several molecular targets and cell surface receptors [e.g., G protein coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs)] may provide cues to its relative pharmacological selectivity and its effects on disease mechanisms. A better understanding of these intricate actions of lithium at a systems level may allow the rational development of better mood stabilizer drugs with enhanced selectivity, efficacy, and lesser side effects.

Cell signaling involves dynamic changes in protein oligomerization leading to the formation of different signaling complexes and modulation of activity. Spatial intensity distribution analysis (SpIDA) is an image analysis method that can directly measure oligomerization and trafficking of endogenous proteins in single cells. Here, we show the use of SpIDA to quantify dimerization/ activation and surface transport of receptor protein kinases-EGF receptor and TrkB-at early stages of their transactivation by several G protein-coupled receptors (GPCRs). Transactivation occurred on the same timescale and was directly limited by GPCR activation but independent of G-protein coupling types. Early receptor protein kinase transactivation and internalization were not interdependent for all receptor pairs tested, revealing heterogeneity between groups of GPCRs. SpIDA also detected transactivation of TrkB by dopamine receptors in intact neurons. By allowing for time and space resolved quantification of protein populations with heterogeneous oligomeric states, SpIDA provides a unique approach to undertake single cell multivariate quantification of signaling processes involving changes in protein interactions, trafficking, and activity.high content analysis | oligomers | monoamine | N-acetyl cystein | brain-derived neurotrophic factor C ell surface receptor signaling involves dynamic spatial and temporal changes in protein oligomeric states, resulting in an intricate choreography of protein-protein interactions balanced with changes in receptor trafficking. For instance, activation of receptor tyrosine kinases (RTKs) by their cognate ligands enhances receptor dimer formation, internalization, and recruitment of monomeric receptors to the cell surface (1). Furthermore, RTKs can also be transactivated by G protein-coupled receptors (GPCRs) under certain circumstances (2-4). However, little is known about the dynamic effects of transactivation on RTK dimerization and surface trafficking. Indeed, the majority of research directed to understanding transactivation has been limited to biochemical assays (2-4) and provides limited information on the dynamics and/or spatial localization of this process within specific regions/compartments of cells/tissue.Understanding receptor dynamics requires methods that can be applied to cells or tissue under physiologically relevant, nonsteady state conditions. Spatial intensity distribution analysis (SpIDA) is a method based on the fitting of fluorescence intensity histograms calculated from conventional laser-scanning confocal images to monitor protein oligomerization in live or fixed cells and tissues (5). By directly monitoring early interactions between endogenous proteins in single cells rather than relying on the detection of downstream signaling molecules, SpIDA potentially offers several advantages over conventional assays used to study cell surface receptor distributions (5). We apply SpIDA and compare it with fluorescence lifetime imaging microscopy (FLIM) to extract information about t...

The associations between cognitive function and neuropathological markers in patients with mild cognitive impairment (MCI) and Alzheimer disease (AD) remain only partly defined. We investigated relationships between antemortem global cognitive scores and β-amyloid (Aβ), tau, TDP-43, synaptic proteins and other key AD neuropathological markers assessed by biochemical approaches in postmortem anterior parietal cortex samples from 36 subjects (12 MCI, 12 AD and 12 not cognitively impaired) from the Religious Orders Study. Overall, the strongest negative correlation coefficients associated with global cognitive scores were obtained for insoluble phosphorylated tau (r2 = −0.484), insoluble Aβ42 (r2 = −0.389) and neurofibrillary tangle counts (r2 = −0.494) (all p < 0.001). Robust inverse associations with cognition scores were also established for TDP-43-positive cytoplasmic inclusions (r2 = −0.476), total insoluble tau (r2 = −0.385) and Aβ plaque counts (r2 = −0.426). Sarkosyl (SK)- or formic acid (FA)-extracted tau showed similar interrelations. On the other hand, synaptophysin (r2 = +0.335), pS403/404 TDP-43 (r2 = +0.265) and septin-3 (r2 = +0.257) proteins positively correlated with cognitive scores. This study suggests that tau and Aβ42 in their insoluble aggregated forms, synaptic proteins and TDP-43 are the markers in the parietal cortex that are most strongly associated with cognitive function. This further substantiates the relevance of investigating these markers to understand the pathogenesis of AD and develop therapeutic tools.

We present computational studies of two homologous mammalian aspartic proteases (calf and camel chymosin) complexed with 16-residue fragments of their native peptide ligands (cow and camel k-casein) and the cross-complexes. Using molecular docking calculations, homology modelling and molecular dynamics simulations, we compare the binding modes of the four systems. The complexes are of industrial interest because camel chymosin has recently been marketed as an alternative to bovine chymosin as an enzyme to clot milk in cheese manufacturing. The camel enzyme has been shown to have 70% higher clotting activity and only 20% of the unspecific protease activity for bovine k-casein as compared to the bovine enzyme. Interestingly, bovine chymosin has a very low proteolytic rate for camel k-casein. The models provide putative atomic coordinates for these complexes, for which there are no available crystallographic or NMR structures, and help to explain some existing experimental results.