Disease relevance of Cam

• A series of phage clones overlapping the single calmodulin gene locus of Drosophila melanogaster has been isolated and the exons of the gene positioned and sequenced within these clones [1].
• Recombinant BmNOS produced in insect cells using baculovirus was found to require NADPH, Ca2+, calmodulin and tetrahydrobiopterin (BH4) for its activity [2].
• Study of the activity of head ganglion cells of larvae of the Drosophila ts-mutant with altered capacity for learning and increased activational properties of calmodulin [3].

Psychiatry related information on Cam

• In vertebrate myosin I isoforms, the light chain is calmodulin, which is thought to regulate motor activity [4].

High impact information on Cam

• We report the characterization of Drosophila Cam mutants and the role of CAM in photoreceptor cell function [5].
• We also analyzed light responses in a variety of mutant and transgenic backgrounds and demonstrate the importance of calmodulin in mediating calcium-dependent negative regulation of phototransduction [5].
• We postulate that there is at least one other type of adenylate cyclase activity that is unaffected by the mutation and insensitive to calcium/calmodulin [6].
• Loss of calcium/calmodulin responsiveness in adenylate cyclase of rutabaga, a Drosophila learning mutant [6].
• This calmodulin localization was dependent on the NINAC (neither inactivation nor afterpotential C) unconventional myosins [7].

Chemical compound and disease context of Cam

• A novel selection strategy, exploiting the CaM tag, was then used to isolate four single chain Fv fragments (scFvs) specific for GP6 from a non-immune phage display library [8].
• The mitotic activity of cells of the head neural ganglion of Drosophila larvae of two genetic lines, the agts 3-mutant line, which possesses increased calmodulin activational properties and altered capacity for learning, and the wild type CS line, serving as a control, was studied [3].

Biological context of Cam

• Prior to death in the first larval instar, Cam nulls show a striking behavioral abnormality (spontaneous backward movement) whereas a mutation, Cam7, that results in a single amino acid change (V91G) produces a very different phenotype: short indented pupal cases and pupal death with head eversion defects [9].
• Biochemical properties of V91G calmodulin: A calmodulin point mutation that deregulates muscle contraction in Drosophila [10].
• Furthermore, a defect in vision resulted when calmodulin was not concentrated in the rhabdomeres, suggesting a role for calmodulin in the regulation of fly phototransduction [7].
• Phosrestin I undergoes the earliest light-induced phosphorylation by a calcium/calmodulin-dependent protein kinase in Drosophila photoreceptors [11].
• We propose that negative feedback of Ca-CaM on Ca2+ release from ryanodine-sensitive stores mediates light adaptation, is essential for light excitation, and keeps the store-operated inward current under a tight control [12].

Anatomical context of Cam

• In the Drosophila retina, calmodulin was concentrated in the photoreceptor cell microvillar structure, the rhabdomere, and was found in lower amounts in the sub-rhabdomeral cytoplasm [7].
• Deletion of the myosin head-like domain or the calmodulin-binding domain of p174 resulted in a similar abnormal cytoskeleton [13].
• In late embryogenesis, maternally derived CaM protein relocalizes dramatically within the nervous system of both wildtype and Cam null embryos-a process that may also involve movement across cell membranes [14].
• Therefore, the distribution of mRNA encoding the calmodulin-sensitive adenylate cyclase in rat brain was examined by in situ hybridization. mRNA for this enzyme is expressed in specific areas of brain that have been implicated in learning and memory, including the neocortex, the hippocampus, and the olfactory system [15].
• When solubilized bovine membranes were first depleted of most of their endogenous CaM by prior chromatography, binding to the CaM column was substantially increased and Ca2+ stimulation of the unbound fraction was somewhat reduced [16].

Associations of Cam with chemical compounds

• The effects of the mutation on free CaM are minor: Calcium binding, and overall secondary and tertiary structure are indistinguishable from those of wild type [10].
• A mutation (Cam7) to the single endogenous calmodulin gene of Drosophila generates a mutant protein with valine 91 changed to glycine (V91G D-CaM) [10].
• We found that the spatial localization of calmodulin depended on binding to both C1 and C2 [17].
• These results suggest that calmodulin binding to both C1 and C2 is required in vivo for termination of phototransduction [17].
• PP7 is not affected by calmodulin and is insensitive to inhibition by okadaic acid, microcystin-LR, calyculin A, and cantharidin [18].
• We identified that lysine 94 located in an EF-hand III is the methylation site in Drosophila calmodulin [19].

Physical interactions of Cam

• Identification and characterization of two distinct calmodulin-binding sites in the Trpl ion-channel protein of Drosophila melanogaster [20].
• Third, E63-1 encodes a novel Ca(2+)-binding protein related to calmodulin [21].
• We have expressed a truncated single-headed Drosophila myosin VIIB construct in the baculovirus-Sf9 system that bound calmodulin light chains [22].
• We conclude that the activation of the Ras cascade may be an important in vivo requisite to the transduction of signals through RIC and that the binding of calmodulin to RIC may negatively regulate this small GTPase [23].
• The two EF hands of the C-domain of androcam bind calcium cooperatively with 40-fold higher average affinity than the corresponding calmodulin sites [24].
• Neuronal expression of a calmodulin-binding deficient V100 uncovers an incomplete rescue at low levels and cellular toxicity at high levels [25].

Enzymatic interactions of Cam

• Here we present biochemical evidence that a CaM PK that phosphorylates arrestin in Limulus eyes is structurally similar to mammalian CaM PK II [26].
• Calcium/calmodulin-dependent protein kinase II phosphorylates and regulates the Drosophila eag potassium channel [27].

Regulatory relationships of Cam

• The eag potassium channel binds and locally activates calcium/calmodulin-dependent protein kinase II [28].
• The cDNA encoding the Trpl protein was initially isolated on the basis that the expressed protein binds calmodulin [20].
• On the other hand, reduction of calmodulin exacerbated the defects caused by activated RIC, thus providing the first functional evidence for interaction of these molecules [23].
• Identification of a cDNA encoding a Drosophila calcium/calmodulin regulated protein phosphatase, which has its most abundant expression in the early embryo [29].

Other interactions of Cam

• The predicted functional consequences of these changes are consonant with the in vivo phenotype, and indicate that D-RyR is one, if not the major, target affected by the V91G mutation in CaM [10].
• Dependence of calmodulin localization in the retina on the NINAC unconventional myosin [7].
• Regulation of the rhodopsin protein phosphatase, RDGC, through interaction with calmodulin [30].
• Two other calmodulin-binding proteins included Pollux, a protein with similarity to a portion of a yeast Rab GTPase activating protein, and Calossin, an enormous protein of unknown function conserved throughout animal phylogeny [31].
• The prototype of calcium-binding protein used for experiments is calmodulin; whether or not calmodulin is also the natural interaction partner of TRP channels is an open question [32].

Analytical, diagnostic and therapeutic context of Cam

• The structure of CaM in a high-affinity complex with a 25-residue peptide of CaMKI (residues 294-318) has been determined by X-ray crystallography at 1.7 A resolution [33].
• The Ca(2+) titration of the (15)N-labeled mutant V136G calmodulin has been monitored using (1)H-(15)N HSQC NMR spectra [34].
• The present work studies the direct interaction of melatonin with intact calcium-saturated CaM both experimentally, by fluorescence and nuclear magnetic resonance spectroscopies, and theoretically, by molecular dynamics simulations [35].
• Comparative structure-based sequence analysis of calmodulin binding regions from various target proteins predicts variable affinities for the interaction of calmodulin with members of the MAGUK protein family [36].
• Northern blot analysis revealed that the two transcripts from the calmodulin gene are differentially expressed during embryogenesis [37].

References