Potent inhibition of Ca2+ release-activated Ca2+ channels and T-lymphocyte activation by the pyrazole derivative BTP2

Ca2+ entry through store-operated Ca2+release-activated Ca2+ (CRAC) channels is essential for T-cell activation and proliferation. Recently, it has been shown that 3,5-bistrifluoromethyl pyrazole (BTP) derivatives are specific inhibitors of Ca2+-dependent transcriptional activity in T-cells (Trevillyan, J. M., Chiou, X. G., Chen, Y. W., Ballaron, S. J., Sheets, M. P., Smith, M. L., Wiedeman, P. E., Warrior, U., Wilkins, J., Gubbins, E. J., Gagne, G. D., Fagerland, J., Carter, G. W., Luly, J. R., Mollison, K. W., and Djuric, S. W. (2001) J. Biol. Chem. 276, 48118-48126). Whereas inhibition of Ca2+ signals was reported for BTP2 (Ishikawa, J., Ohga, K., Yoshino, T., Takezawa, R., Ichikawa, A., Kubota, H., and Yamada, T. (2003) J. Immunol. 170, 4441-4449), it was not found for BTP3 (Chen, Y., Smith, M. L., Chiou, G. X., Ballaron, S., Sheets, M. P., Gubbins, E., Warrior, U., Wilkins, J., Surowy, C., Nakane, M., Carter, G. W., Trevillyan, J. M., Mollison, K., and Djuric, S. W. (2002) Cell. Immunol. 220, 134-142). We show that BTP2 specifically inhibits CRAC channels in T-cells with an IC(50) of approximately 10 nm. It does not interfere with other mechanisms important for Ca2+ signals in T-cells, including Ca2+ pumps, mitochondrial Ca2+ signaling, endoplasmic reticulum Ca2+ release, and K+ channels. BTP2 inhibits Ca2+ signals in peripheral blood T-lymphocytes (in particular in CD4+ T-cells) and in human Jurkat T-cells. Inhibition of Ca2+ signals is independent of the stimulation method as Ca2+ entry was blocked following stimulation with anti-CD3, which activates the T-cell receptor, and also following stimulation with thapsigargin or inositol 1,4,5-trisphosphate. BTP2 also inhibited Ca2+-dependent gene expression (interleukins 2 and 5 and interferon gamma) and proliferation of T-lymphocytes with similar IC(50) values. BTP2 is the first potent and specific inhibitor of CRAC channels in primary T-lymphocytes. The inhibition of CRAC channels as well as Ca2+-dependent signal transduction with similar IC(50) values in T-lymphocytes emphasizes the importance of CRAC channel activity during T-cell activation. Furthermore, BTP2 could prove to be a tool to finally unmask the molecular identity of CRAC channels.

Formation of a unilateral form deprivation myopia (FDM) due to a congenital eyelid entropium with a consecutive corneal ulcer: an illustrated case report

Eye growth is regulated by a precise, sharp image of a distant object on the photoreceptor layer. A variety of laboratory investigations report that translucent occluders may induce axial eye elongation in animals. This axial growth is also called form deprivation myopia (FDM). In our pediatric ophthalmology clinic we observed the clinical correlate of FDM in a male infant with unilateral corneal ulcer due to a congenital tarsal malformation. Examination in the postnatal period under anesthesia revealed identical axial length in both eyes. Refraction of the affected eye could not be measured due to severe corneal ulcer. During an observation period of two years, the deep corneal opacification of the affected eye induced unilateral disproportionate axial elongation with formation of myopia. Formation of FDM may complicate treatment of amblyopia following unilateral media opacification. Periodic measurements of refraction should be performed to allow appropriate correction.

[Does the type of lens influence stereoscopic vision]

PURPOSE

Age and monofocal intraocular lens (IOL) are assumed to reduce the quality of stereopsis, whereas multifocal intraocular lenses (MIOL) are supposed to provide better random dot stereopsis than monofocal IOL. The following study investigates whether and how the different IOL types (including the different existing principles of MIOL) influence stereopsis.

PATIENTS AND METHODS

We included 153 persons from six groups (young and elder phakic subjects, patients with bilateral monofocal IOL, with bilateral diffractive MIOL, with bilateral refractive MIOL, and with unilateral diffractive/refractive MIOL). Stereopsis measurements were performed using the Pola test with a two-dimensional and a random dot test for far and near distances and the results for near distance were compared with the Lang random dot, two-dimensional Titmus, and the Monjé real three-dimensional tests. Near and distance monocular and binocular visual acuity and orthoptic examinations had been previously carried out.

RESULTS

Of the young phakic subjects, 81-92% correctly perceived the Pola test figures, and 100% did so in the Lang, Titmus, and Monjé tests. Of the elder phakic subjects, 36-73% correctly perceived the Pola test, and 52-88% did so in the Lang, Titmus, and Monjé tests. Of the patients with bilateral monofocal IOL, 19-62% perceived the Pola test figures, as did 30-61% of the patients with bilateral diffractive MIOL, 12-53% of the patients with bilateral refractive MIOL, and 5-29% of the patients with unilateral diffractive/refractive MIOL.

CONCLUSION

All patients with bilateral mono- or different multifocal IOL had good binocular vision in far and near distance including random dot stereopsis.

Dictyostelium myosin IK is involved in the maintenance of cortical tension and affects motility and phagocytosis

Dictyostelium discoideum myosin Ik (MyoK) is a novel type of myosin distinguished by a remarkable architecture. MyoK is related to class I myosins but lacks a cargo-binding tail domain and carries an insertion in a surface loop suggested to modulate motor velocity. This insertion shows similarity to a secondary actin-binding site present in the tail of some class I myosins, and indeed a GST-loop construct binds actin. Probably as a consequence, binding of MyoK to actin was not only ATP- but also salt-dependent. Moreover, as both binding sites reside within its motor domain and carry potential sites of regulation, MyoK might represent a new form of actin crosslinker. MyoK was distributed in the cytoplasm with a significant enrichment in dynamic regions of the cortex. Absence of MyoK resulted in a drop of cortical tension whereas overexpression led to significantly increased tension. Absence and overexpression of MyoK dramatically affected the cortical actin cytoskeleton and resulted in reduced initial rates of phagocytosis. Cells lacking MyoK showed excessive ruffling, mostly in the form of large lamellipodia, accompanied by a thicker basal actin cortex. At early stages of development, aggregation of myoK null cells was slowed due to reduced motility. Altogether, the data indicate a distinctive role for MyoK in the maintenance and dynamics of the cell cortex.

[Strabismus and diplopia as complications after cataract surgery with IOL implantation]

In our Department of Orthoptics we have seen an increasing number of patients suffering from diplopia after cataract surgery with IOL implantation. Between 1993 and 1997 the total number of patients with this problem was 24 (2.7 % of all patients, mean age 71 years, age range 38-88). We addressed the question of whether there is a common pattern of motility dysfunction.

METHODS

After evaluation of the clinical history and the basic ophthalmological findings the following parameters were examined: binocular function (Bagolini test), squint angles (Maddox cross), ocular motility.

RESULTS

The 24 patients could be divided up into three groups. Group 1 consisted of 9 patients (mean age 82 years, range 64-88) who complained about diplopia because of strabismus incomitans with vertical deviation and restricted motility on the first day after surgery. In 8 of the 9 patients strabismus surgery was done. Group II consisted of 10 patients (mean age 66 years, range 38-77) who noticed diplopia and strabismus within 7 days after surgery. We found various kinds of heterotropia. Seven of these patients were operated on and two had a prism correction. Group III consisted of 5 patients (mean age 67 years, range 61-78). Their already known strabismus paralyticus or concomitans deteriorated, leading to diplopia in some cases. All patients in this group were operated on.

DISCUSSION

For group I we believe that retro-, para- or peribulbar anesthesia caused the motility dysfunction. In groups II and III it is unlikely that local anesthesia had a causative role. The prolonged disruption of binocular vision and the abrupt change in the sensory situation after the cataract operation with lens implantation may be the leading causes for strabismus or deterioration of a preexisting strabism, respectively.

CONCLUSIONS

These patients need a subtil meticulous diagnostic work-up and follow-up because of the possibility of early surgical therapy, which has a good prognosis. Evaluation of binocular vision and eye movements prior to cataract surgery appears to be helpful for later strabismic surgery.

How many is enough? Exploring the myosin repertoire in the model eukaryote Dictyostelium discoideum

The cytoplasm of eukaryotic cells is a very complex milieu and unraveling how its unique cytoarchitecture is achieved and maintained is a central theme in modern cell biology. It is crucial to understand how organelles and macro-complexes of RNA and/or proteins are transported to and/or maintained at their specific cellular locations. The importance of filamentous-actin-directed myosin-powered cargo transport was only recently realized, and after an initial explosion in the identification of new molecules, the field is now concentrating on their functional dissection. Direct connections of myosins to a variety of cellular tasks are now slowly emerging, such as in cytokinesis, phagocytosis, endocytosis, polarized secretion and exocytosis, axonal transport, etc. Unconventional myosins have been identified in a wide variety of organisms, making the presence of actin and myosins a hallmark of eukaryotism. The genome of S. cerevisiae encodes only five myosins, whereas a mammalian cell has the capacity to express between two and three dozen myosins. Why is it so crucial to arrive at this final census? The main questions that we would like to discuss are the following. How many distinct myosin-powered functions are carried out in a typical higher eukaryote? Or, in other words, what is the minimal set of myosins essential to accomplish the multitude of tasks related to motility and intracellular dynamics in a multicellular organism? And also, as a corollary, what is the degree of functional redundancy inside a given myosin class? In that respect, the choice of a model organism suitable for such an investigation is more crucial than ever. Here we argue that Dictyostelium discoideum is affirming its position as an ideal system of intermediate complexity to study myosin-powered trafficking and is or will soon become the second eukaryote for which complete knowledge of the whole repertoire of myosins is available.

A potentially exhaustive screening strategy reveals two novel divergent myosins in Dictyostelium

In recent years, the myosin superfamily has kept expanding at an explosive rate, but the understanding of their complex functions has been lagging. Therefore, Dictyostelium discoideum, a genetically and biochemically tractable eukaryotic amoeba, appears as a powerful model organism to investigate the involvement of the actomyosin cytoskeleton in a variety of cellular tasks. Because of the relatively high degree of functional redundancy, such studies would be greatly facilitated by the prior knowledge of the whole myosin repertoire in this organism. Here, we present a strategy based on PCR amplification using degenerate primers and followed by negative hybridization screening which led to the potentially exhaustive identification of members of the myosin family in D. discoideum. Two novel myosins were identified and their genetic loci mapped by hybridization to an ordered YAC library. Preliminary inspection of myoK and myoM sequences revealed that, despite carrying most of the hallmarks of myosin motors, both molecules harbor features surprisingly divergent from most known myosins.

Unconventional myosins at the crossroad of signal transduction and cytoskeleton remodeling

The cytoplasm of eukaryotic cells is a complex milieu and unraveling how its unique cytoarchitecture is achieved and maintained is a central theme in modern cell biology. The actin cytoskeleton is essential for the maintenance of cell shape and locomotion, and also provides tracks for active intracellular transport. Myosins, the actin-dependent motor proteins form a superfamily of at least 15 structural classes and have been identified in a wide variety of organisms, making the presence of actin and myosins a hallmark feature of eukaryotes. Direct connections of myosins to a variety of cellular tasks are now emerging, such as in cytokinesis, phagocytosis, endocytosis, polarized secretion and exocytosis, axonal transport. Recent studies reveal that myosins also play an essential role in many aspects of signal transduction and neurosensation.