Live cell imaging has revealed the rapid mobility of steroid hormone receptors within nuclei and their dynamic exchange at transcriptionally active target sites. Although a number of other proteins ...have been shown to be highly mobile within nuclei, the identity of soluble factors responsible for orchestrating nuclear trafficking remains unknown. We have developed a previously undescribed in situ subnuclear trafficking assay that generates transcriptionally active nuclei, which are depleted of soluble factors required for the nuclear mobility of glucocorticoid (GR) and progesterone receptors (PR). Using this system and a fluorescence recovery after photobleaching technique, we demonstrate that nuclear mobility of GR recovered on incubation with reticulocyte lysate was inhibited by geldanamycin, a drug that blocks the chaperone activity of heat-shock protein 90. Direct proof of molecular chaperone involvement in steroid receptor subnuclear trafficking was provided by the ATP-dependent recovery of nuclear mobility of GR and PR on incubation with various combinations of purified chaperone and/or cochaperone proteins. Additionally, for both receptors, the inclusion of hormone during the recovery period leads to a retardation of nuclear mobility. Thus, our results provide a description of soluble nuclear mobility factors and furthermore demonstrate a previously unrecognized role for molecular chaperones in the regulation of steroid receptor function within the nucleus.
Abstract Patellofemoral pain (PFP) may be related to unfavorable knee joint loading. Delayed and/or reduced activity of vastus medialis obliquus (VMO) and different movement patterns have been ...identified in individuals with PFP in some studies, whereas other studies have failed to show a difference compared to non-affected controls. The discrepancy between study results may depend on the different tasks that have been investigated. No previous study has investigated these variables in postural responses to unpredictable perturbations in PFP. Whole body three dimensional kinematics and surface EMG of quadriceps muscles activation was studied in postural responses to unpredictable support surface translations in 17 women with PFP who were pain free at the time of testing, and 17 matched healthy controls. The results of the present study showed earlier onset of VMO activity and associated changes in kinematics to anterior platform translation in the PFP subjects. We suggest that the relative timing between the portions quadriceps muscles may be task specific and part of an adapted response in attempt to reduce knee joint loading. This learned response appears to remain even when the pain is no longer present.
Abstract A recently described family of “orphan” receptors, called Mas-related G-protein-coupled receptors (Mrg), is preferentially expressed in small nociceptive neurons of the rodent and human ...dorsal root ganglia (DRG). Mrg are activated by high affinity peptide fragments derived from the proenkephalin A gene, e.g. BAM22 (bovine adrenal medullary). To study the histological distribution and functional properties of these receptors, we combined confocal immunohistochemistry in rat DRG and dermis whole mounts, using new antibodies against the rat Mas-related G-protein-coupled receptor C (MrgC), with single-fiber recordings and neurochemical experiments using isolated hind-paw skin and sciatic nerve. In lumbar DRG we found cytoplasmic MrgC labeling mainly in small- and medium-sized neurons; coexpression with isolectin B4 (46%) and transient receptor potential vanilloid receptor 1 channel protein (TRPV1) (52%) occurred frequently, whereas calcitonin gene-related peptide (CGRP) was rarely colocalized with MrgC in DRG (11%) and dermal nerve fibers (6%). One of the MrgC agonists, BAM22, more than doubled the heat-induced cutaneous CGRP release from rat and mouse skin. The effect of BAM22, also known to activate opioid receptors, was further enhanced by combination with naloxone that had no effect on its own. This sensitizing effect proved to be independent of secondary prostaglandin formation, mast cell degranulation, protein kinase C (PKC) activation and independent of TRPV1. Nonetheless, the capsaicin-induced CGRP release was also sensitized. Receptive fields of 26 mechano-heat sensitive C-fibers were treated with MrgC agonists. Only one unit was strongly and repeatedly excited and showed a profound sensitization to heat upon BAM22+naloxone. Two other established MrgC agonists (γ2-melanocyte stimulating hormone and BAM8-22) were ineffective. Thus, BAM22 sensitizes the capsaicin- and heat-induced CGRP release in an apparently MrgC-unrelated way. The sensitization to heat appears unusually resistant against pharmacological interventions and does not involve TRPV1.
Crc (catabolite repression control) protein of Pseudomonas aeruginosa has shown to be involved in carbon regulation of several pathways. In this study, the role of Crc in catabolite repression ...control has been studied in Pseudomonas putida. The bkd operons of P. putida and P. aeruginosa encode the inducible multienzyme complex branched-chain keto acid dehydrogenase, which is regulated in both species by catabolite repression. We report here that this effect is mediated in both species by Crc. A 13-kb cloned DNA fragment containing the P. putida crc gene region was sequenced. Crc regulates the expression of branched-chain keto acid dehydrogenase, glucose-6-phosphate dehydrogenase, and amidase in both species but not urocanase, although the carbon sources responsible for catabolite repression in the two species differ. Transposon mutants affected in their expression of BkdR, the transcriptional activator of the bkd operon, were isolated and identified as crc and vacB (rnr) mutants. These mutants suggested that catabolite repression in pseudomonads might, in part, involve control of BkdR levels.
For treatment of various knee disorders, muscles are trained in open or closed kinetic chain tasks. Coordination between the heads of the quadriceps muscle is important for stability and optimal ...joint loading for both the tibiofemoral and the patellofemoral joint. The aim of this study was to examine whether the quadriceps femoris muscles are activated differently in open versus closed kinetic chain tasks.
Ten healthy men and women (mean age 28.5 +/- 0.7) extended the knees isometrically in open and closed kinetic chain tasks in a reaction time paradigm using moderate force. Surface electromyography (EMG) recordings were made from four different parts of the quadriceps muscle. The onset and amplitude of EMG and force data were measured.
In closed chain knee extension, the onset of EMG activity of the four different muscle portions of the quadriceps was more simultaneous than in the open chain. In open chain, rectus femoris (RF) had the earliest EMG onset while vastus medialis obliquus was activated last (7 +/- 13 ms after RF EMG onset) and with smaller amplitude (40 +/- 30% of maximal voluntary contraction (MVC)) than in closed chain (46 +/- 43% MVC).
Exercise in closed kinetic chain promotes more balanced initial quadriceps activation than does exercise in open kinetic chain. This may be of importance in designing training programs aimed toward control of the patellofemoral joint.
Topically applied camphor elicits a sensation of cool, but nothing is known about how it affects cold temperature sensing. We found that camphor sensitizes a subpopulation of menthol-sensitive native ...cutaneous nociceptors in the mouse to cold, but desensitizes and partially blocks heterologously expressed TRPM8 (transient receptor potential cation channel subfamily M member 8). In contrast, camphor reduces potassium outward currents in cultured sensory neurons and, in cold nociceptors, the cold-sensitizing effects of camphor and menthol are additive. Using a membrane potential dye-based screening assay and heterologously expressed potassium channels, we found that the effects of camphor are mediated by inhibition of Kv7.2/3 channels subtypes that generate the M-current in neurons. In line with this finding, the specific M-current blocker XE991 reproduced the cold-sensitizing effect of camphor in nociceptors. However, the M-channel blocking effects of XE991 and camphor are not sufficient to initiate cold transduction but require a cold-activated inward current generated by TRPM8. The cold-sensitizing effects of XE991 and camphor are largest in high-threshold cold nociceptors. Low-threshold corneal cold thermoreceptors that express high levels of TRPM8 and lack potassium channels are not affected by camphor. We also found that menthol--like camphor--potently inhibits Kv7.2/3 channels. The apparent functional synergism arising from TRPM8 activation and M-current block can improve the effectiveness of topical coolants and cooling lotions, and may also enhance TRPM8-mediated analgesia.
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