Different modes of interaction of calmodulin with its target enzymes

Why thioridazine in combination with antibiotics cures extensively drug-resistant Mycobacterium tuberculosis infections

Thioridazine (TDZ) in combination with antibiotics to which extensively drug-resistant Mycobacterium tuberculosis (XDR-TB) is initially resistant yields a cure. This is due to the fact that TDZ enhances the killing of intracellular M. tuberculosis by non-killing macrophages, inhibits the genetic expression of efflux pumps of M. tuberculosis that extrude antibiotics prior to reaching their intended targets, and inhibits the activity of existing efflux pumps that contribute to the multidrug-resistant phenotype of M. tuberculosis. The combination of these effects of TDZ probably contributes to the successful recent cures of XDR-TB cases when the phenothiazine TDZ is used in combination with antibiotics to which the patient with XDR-TB was initially unresponsive.

RGS proteins provide biochemical control of agonist-evoked [Ca2+]i oscillations

Agonist-evoked [Ca2+]i oscillations have been considered a biophysical phenomenon reflecting the regulation of the IP3 receptor by [Ca2+]i. Here we show that [Ca2+]i oscillations are a biochemical phenomenon emanating from regulation of Ca2+ signaling by the regulators of G protein signaling (RGS) proteins. [Ca2+]i oscillations evoked by G protein-coupled receptors require the action of RGS proteins. Inhibition of endogenous RGS protein action disrupted agonist-evoked [Ca2+]i oscillations by a stepwise conversion to a sustained response. Based on these findings and the effect of mutant RGS proteins and anti-RGS protein antibodies on Ca2+ signaling, we propose that RGS proteins within the G protein-coupled receptor complexes provide a biochemical control of [Ca2+]i oscillations.

Traumatic optic neuropathy

Knowledge concerning the pathophysiologic mechanisms of traumatic optic neuropathy is limited. The optic nerve is a tract of the brain. Therefore, the cellular and biochemical pathophysiology of brain and spinal cord trauma and ischemia provide insight into mechanisms that may operate in traumatic optic neuropathy. The dosage of methylprednisolone (30 mg/kg/6 hours) which was successful in the National Acute Spinal Cord Injury Study 2 (NASCIS 2) evolved from the unique pharmacology of corticosteroids as antioxidants. The management of traumatic optic neuropathy rests on an accurate diagnosis which begins with a comprehensive clinical assessment and appropriate neuroimaging. The results of medical and surgical strategies for treating this injury have not been demonstrated to be better than those achieved without treatment. The spinal cord is a mixed grey and white matter tract of the brain in contrast to the optic nerve which is a pure white matter tract. The treatment success seen with methylprednisolone in the NASCIS 2 study may not generalize to the treatment of traumatic optic neuropathy. Conversely, if the treatment does generalize to the optic nerve, NASCIS 2 data suggests that treatment must be started within eight hours of injury, making traumatic optic neuropathy one of the true ophthalmic emergencies. Given the uncertainties in the treatment, ophthalmologists involved in the management of traumatic optic neuropathy are encouraged to participate in the collaborative study of traumatic optic neuropathy.

A continuous spectrophotometric assay for the activation of plant NAD kinase by calmodulin, calcium(II), and europium(III) ions

A continuous spectrophotometric assay has been developed to quantify the calmodulin, calcium(II) ion, and europium(III) ion dependence of the activation of NAD kinase from pea seedlings. Experimental enzyme activation data are compared with the theoretical curves for the binding of calcium(II) ions to the individual calcium binding sites of calmodulin. These results indicate that the binding of three calcium(II) ions is necessary for activation of plant NAD kinase. Further studies demonstrate that europium(III) ions can replace calcium(II) ions in calmodulin with retention of its ability to activate NAD kinase.