The cytoplasmic domain of MT1-MMP is dispensable for migration augmentation but necessary to mediate viability of MCF-7 breast cancer cells

Membrane-type-1 Matrix Metalloproteinase (MT1-MMP) is a multifunctional protease that regulates ECM degradation, proMMP-2 activation, and varied cellular processes including migration and viability. MT1-MMP is believed to be a central mediator of tumourigenesis whose role is dictated by its functionally distinct protein domains. Both the localization and signal transduction capabilities of MT1-MMP are dependent on its cytoplasmic domain, exemplifying diverse regulatory functions. To further our understanding of the multifunctional contributions of MT1-MMP to cellular processes, we overexpressed cytoplasmic domain altered constructs in MCF-7 breast cancer cells and analyzed migration and viability in 2D culture conditions, morphology in 3D Matrigel culture, and tumorigenic ability in vivo. We found that the cytoplasmic domain was not needed for MT1-MMP mediated migration promotion, but was necessary to maintain viability during serum depravation in 2D culture. Similarly, during 3D Matrigel culture the cytoplasmic domain of MT1-MMP was not needed to initiate a protrusive phenotype, but was necessary to prevent colony blebbing when cells were serum deprived. We also tested in vivo tumorigenic potential to show that cells expressing cytoplasmic domain altered constructs demonstrated a reduced ability to vascularize tumours. These results suggest that the cytoplasmic domain regulates MT1-MMP function in a manner required for cell survival, but is dispensable for cell migration.     

Repeated triggering of sporulation in Bacillus subtilis selects against a protein that affects the timing of cell division

Bacillus subtilis sporulation is a last-resort phenotypical adaptation in response to starvation. The regulatory network underlying this developmental pathway has been studied extensively. However, how sporulation initiation is concerted in relation to the environmental nutrient availability is poorly understood. In a fed-batch fermentation set-up, in which sporulation of ultraviolet (UV)-mutagenized B. subtilis is repeatedly triggered by periods of starvation, fitter strains with mutated tagE evolved. These mutants display altered timing of phenotypical differentiation. The substrate for the wall teichoic acid (WTA)-modifying enzyme TagE, UDP-glucose, has recently been shown to be an intracellular proxy for nutrient availability, and influences the timing of cell division. Here we suggest that UDP-glucose also influences timing of cellular differentiation.     

Neurogenetic interactions and aberrant behavioral co-morbidity of attention deficit hyperactivity disorder (ADHD): dispelling myths

Background

Attention Deficit Hyperactivity Disorder, commonly referred to as ADHD, is a common, complex, predominately genetic but highly treatable disorder, which in its more severe form has such a profound effect on brain function that every aspect of the life of an affected individual may be permanently compromised. Despite the broad base of scientific investigation over the past 50 years supporting this statement, there are still many misconceptions about ADHD. These include believing the disorder does not exist, that all children have symptoms of ADHD, that if it does exist it is grossly over-diagnosed and over-treated, and that the treatment is dangerous and leads to a propensity to drug addiction. Since most misconceptions contain elements of truth, where does the reality lie?

Results

We have reviewed the literature to evaluate some of the claims and counter-claims. The evidence suggests that ADHD is primarily a polygenic disorder involving at least 50 genes, including those encoding enzymes of neurotransmitter metabolism, neurotransmitter transporters and receptors. Because of its polygenic nature, ADHD is often accompanied by other behavioral abnormalities. It is present in adults as well as children, but in itself it does not necessarily impair function in adult life; associated disorders, however, may do so. A range of treatment options is reviewed and the mechanisms responsible for the efficacy of standard drug treatments are considered.

Conclusion

The genes so far implicated in ADHD account for only part of the total picture. Identification of the remaining genes and characterization of their interactions is likely to establish ADHD firmly as a biological disorder and to lead to better methods of diagnosis and treatment.

     

Modulation of K+-channels in p-neurones of the leech CNS by phosphorylation

Two types of potassium channels of identified (p-) neurones of the leech (Hirudo medicinalis) were investigated by using the patch-clamp technique. The openstate probability of these channels in cell-attached patches can be reduced by addition of 5-hydroxytryptamine to the bath solution. After excising the patches the application of alkaline phosphatase to the cytosolic face of the patch increases the open probability. The 5-HT_1A-receptor agonist buspirone mimics the effect of 5-HT. Our experiments show that the effect of 5-HT might be due to a channel phosphorylation via a 5-HT_1A-receptor subtype.     

Melittin and a chemically modified trichotoxin form alamethicin-type multi-state pores

The bee venom constituent, melittin, is structurally and functionally related to alamethicin. By forming solvent-free planar bilayers of small area (approx. 100 microns 2) on the tip of fire-polished glass pipettes we could observe single melittin pores in these membranes. An increase in the applied voltage induced further non-integral conductance levels. This indicates that melittin forms multi-level pores similar to those formed by alamethicin. Trichotoxin A40, an antibiotic analogue of alamethicin, also induces a voltage-dependent bilayer conductivity, but no stable pore states are resolved. However, chemical modification of the C-terminal molecule part by introduction of a dansyl group leads to a steeper voltage-dependence and pore state stabilization. Comparing structure and activity of several natural and synthetic amphiphilic polypeptides, we conclude that a lipophilic, N-terminal alpha-helical part of adequate length (dipole moment) and a large enough hydrophilic, C-terminal region are sufficient prerequisites for voltage-dependent formation of multi-state pores.