We used electron microscopic immunocytochemistry to study the distribution of calmodulin in rat sciatic nerve. Calmodulin immunoreactivity was found throughout the axoplasmic matrix, but particularly along microtubules. Schwann cell cytoplasm and nuclei demonstrated immunoreactivity, while compact myelin did not. There was particularly intense immuno-gold deposition within Schmidt Lanterman cle...

Calmodulin plays a vital role in mediating bidirectional synaptic plasticity by activating either calcium/calmodulin-dependent protein kinase II (CaMKII) or protein phosphatase 2B (PP2B) at different calcium concentrations. We propose an allosteric model for calmodulin activation, in which binding to calcium facilitates the transition between a low-affinity [tense (T)] and a high-affinity [rela...

Membrane remodeling by BAR (Bin, Amphiphysin, RVS) domain-containing proteins, such as endophilins and amphiphysins, is integral to the process of endocytosis. However, little is known about the regulation of endocytic BAR domain activity. We have identified an interaction between the yeast Rvs167 N-BAR domain and calmodulin. Calmodulin-binding mutants of Rvs167 exhibited defects in endocytic v...

Calmodulin is a ubiquitous Ca2+ binding protein that binds to ryanodine rectors (RyR) and is thought to modulate its activity. Here we evaluated the effects of recombinant calmodulin on the rate of occurrence and spatial properties of Ca2+ sparks as an assay of activation in saponin-permeabilized mouse myofibers. Control myofibers exhibited a time-dependent increase and subsequent decrease in s...

Three nuclear subfractions were prepared from isolated hepatocytes nuclei. The calmodulin content in whole nuclei was 79 ng/mg of protein. The soluble fraction obtained after digestion of the nuclei with DNase I and RNase A (S1 fraction) contained 252 ng of calmodulin/mg of protein. The pellet obtained after the digestion with nucleases was treated with 1.6 M NaCl, and the soluble fraction and ...

Engagement of platelet membrane glycoprotein (GP) Ib-IX-V by von Willebrand factor triggers Ca(++)-dependent activation of alphaIIbbeta3, resulting in (patho)physiological thrombus formation. It is demonstrated here that the cytoplasmic domain of GPIb-IX-V associates with cytosolic calmodulin. First, an anti-GPIbalpha antibody coimmunoprecipitated GPIb-IX and calmodulin from platelet lysates. F...

Calmodulin derivatives, specifically biotinylated in domains I and III, were synthesized to address the structures of calmodulin necessary for binding to its target enzymes in active conformations. By binding avidin to these biotinylated calmodulins, the role of specific sequences of the calmodulin molecule in target enzyme interactions could then be evaluated. The role of domain I in these int...

The calmodulin contents of rabbit brain, lung, kidney and liver, of bovine aorta and uterus, and of chicken gizzard have been determined. 2. The calmodulin in all of these tissues has been shown to be present in the form of very stable complexes with several other proteins. 3. A calmodulin-binding protein of mol.wt. 22 000 has been purified in high yield from bovine brain. It has been shown to ...

Calmodulin is phosphorylated in vitro by the insulin-receptor tyrosine kinase and a variety of serine/threonine kinases. Here we report that insulin stimulates the phosphorylation of calmodulin on average 3-fold in intact rat hepatocytes. Although calmodulin is constitutively phosphorylated, insulin increases phosphate incorporation into serine, threonine and tyrosine residues. We demonstrate t...

The activity of the Ca2+/calmodulin-dependent protein kinase IV/Gr (CaMKIV/Gr) is shown to be strictly regulated by phosphorylation of three residues both in vitro and in response to antigen receptor-mediated signaling in lymphocytes. One residue, Thr-200, is indispensable for enhancement of Ca2+/calmodulin-dependent basal activity by CaMKIV/Gr kinase. This event requires Ca2+/calmodulin in the...