Preface Intermediate filaments (IFs) are cytoskeletal and nucleoskeletal structures that provide mechanical and stress-coping resilience to cells, contribute to subcellular and tissue-specific biological functions, and facilitate intracellular communication. IF proteins, including nuclear lamins and cytoplasmic keratins, vimentin, desmin, neurofilaments, and glial fibrillary acidic protein, undergo various functionally important post-translational modifications (PTMs). Proteomic advances highlight the enormous complexity of IF PTMs, which include phosphorylation, glycosylation, sumoylation, acetylation, and prenylation, as well as their ability to regulate IF proteins, and are likely to reveal novel modifications. We would like to keep the original statement, since the revised version seems to imply that proteomic advances provide insight into the ability of PTMs to regulate IF proteins, which is not the case. Future studies will need to characterize their on–off mechanisms, cross-talk, and utility as biomarkers and targets for diseases involving the IF cytoskeleton.

The vimentin gene ( VIM) encodes one of the 71 human intermediate filament (IF) proteins, which are the building blocks of highly ordered, dynamic, and cell type-specific fiber networks. Vimentin is a multi-functional 466 amino acid protein with a high degree of evolutionary conservation among vertebrates. Vim −/− mice, though viable, exhibit systemic defects related to development and wound repair, which may have implications for understanding human disease pathogenesis. Vimentin IFs are required for the plasticity of mesenchymal cells under normal physiological conditions and for the migration of cancer cells that have undergone epithelial–mesenchymal transition. Although it was observed years ago that vimentin promotes cell migration, the molecular mechanisms were not completely understood. Recent advances in microscopic techniques, combined with computational image analysis, have helped illuminate vimentin dynamics and function in migrating cells on a precise scale. This review includes a brief historical account of early studies that unveiled vimentin as a unique component of the cell cytoskeleton followed by an overview of the physiological vimentin functions documented in studies on Vim −/− mice. The primary focus of the discussion is on novel mechanisms related to how vimentin coordinates cell migration. The current hypothesis is that vimentin promotes cell migration by integrating mechanical input from the environment and modulating the dynamics of microtubules and the actomyosin network. These new findings undoubtedly will open up multiple avenues to study the broader function of vimentin and other IF proteins in cell biology and will lead to critical insights into the relevance of different vimentin levels for the invasive behaviors of metastatic cancer cells.

SUMMARY The concentrations of free amino acids in plasma, CSF and in vivo dialysates of peripheral blood (neck sac fluid) and central nervous tissue (brain sac fluid) from each of five dogs (neck sac fluid from four of five dogs) were determined by ion‐exchange chromatography. Dialysates were obtained by implanting small dialysis sacs filled with a dextran‐saline solution into the subcutaneous tissue of the neck or the parenchyma of the brain at least 10 weeks before sample collection. The mean plasma concentration of most amino acids was within the range of values reported in the literature for human or dog plasma. The concentrations of most amino acids were higher in the neck sac fluid than in plasma; this discrepancy, however, was, for the most part, small and could most likely be accounted for by falling plasma free amino acid levels prior to sample taking. Previous conclusions that the CSF concentrations of most amino acids are lower than plasma concentrations are confirmed, although the present work indicates that there may be considerable individual variation in the CSF/plasma distribution ratio with respect to most amino acids. In the brain sac fluid the concentration of nearly every amino acid was consistently higher than that in CSF and lower than that in the neck sac fluid. The potassium concentration in the brain sac fluid was significantly higher than, and the total osmolality significantly lower than, those in the neck sac fluid. On the assumption that the brain sac fluid represents a dialysate of the brain extracellular fluid, these results contradict recent findings (Bito and Davson, 1965; 1966) indicating that the potassium concentration of the cortex extracellular fluid is lower than that of ventricular or cisterna magna CSF and certainly lower than that of plasma. Because of this and on the basis of consideration of the reaction of the brain to a foreign body, the possibility that the implanted brain sac lay on the‘blood side’of the bloodbrain barrier was suggested. Some implications of this possibility are discussed.

2-Arachidonyl glycerol (2-AG) is an endogenous arachidonic acid derivative that binds cannabinoid receptors CB1 and CB2 and is hence termed an endocannabinoid. 2-AG also modulates a variety of immunological responses, including expression of the autocrine/paracrine T cell growth factor interleukin (IL)-2. The objective of the present studies was to determine the mechanism responsible for IL-2 suppression by 2-AG. Because of the labile properties of 2-AG, 2-AG ether, a nonhydrolyzable analog of 2-AG, was also used. Both 2-AG and 2-AG ether suppressed IL-2 expression independently of CB1 and CB2, as demonstrated in leukocytes derived from CB1/CB2-null mice. Moreover, we demonstrated that both 2-AG and 2-AG ether treatment activated peroxisome proliferator-activated receptor ␥ (PPAR␥), as evidenced by forced differentiation of 3T3-L1 cells into adipocytes, induction of aP2 mRNA levels, and activation of a PPAR␥-specific luciferase reporter in transiently transfected 3T3-L1 cells. Consequently, the putative role of PPAR␥ in IL-2 suppression by 2-AG and 2-AG ether was examined in Jurkat T cells. Concordant with PPAR␥ involvement, the PPAR␥-specific antagonist 2-chloro-5-nitro-N-(4-pyridyl)-benzamide (T0070907) blocked 2-AG-and 2-AG ether-mediated IL-2 suppression. Likewise, 2-AG suppressed the transcriptional activity of two transcription factors crucial for IL-2 expression, nuclear factor of activated T cells and nuclear factor B, in the absence but not in the presence of T0070907. 2-AG treatment also induced PPAR␥ binding to a PPAR response element in activated Jurkat T cells. Together, the aforementioned studies identify PPAR␥ as a novel intracellular target of 2-AG, which mediates the suppression of IL-2 by 2-AG in a manner that is independent of CB1 and/or CB2.