A soluble calcium-binding protein from the terrestrial annelidLumbricus terrestris L

Soluble calcium-binding proteins (SCBPs) of the earthworm Lumbricus terrestris: possible role as relaxation factors in muscle

The soluble Ca²⁺-binding protein (SCBP) from the earthworm Lumbricus terrestris was analyzed with regard to its role as a soluble muscle relaxation factor. The actomyosin ATPase activity was inhibited by the addition of decalcified SCBP as it binds Ca²⁺ stronger than the regulatory proteins associated with the actomyosin. Competitive ⁴⁵Ca²⁺-binding assays with decalcified actomyosin and SCBP showed that ⁴⁵Ca²⁺ is first bound to actomyosin and is subsequently taken over by SCBP with increasing incubation time. Ca²⁺ competition experiments carried out with ⁴⁵Ca²⁺ loaded SCBP and fragmented sarcoplasmic reticulum vesicles revealed that ⁴⁵Ca²⁺ bound to SCBP can be deprived by the ATP-dependent Ca²⁺ uptake of the sarcoplasmic reticulum. Furthermore, experiments in a diffusion chamber showed that the addition of SCBP significantly enhances the ⁴⁵Ca²⁺ flux in a concentration dependent manner. The amount of the Ca²⁺ flux increase tends to reach a maximum value of about 70%. With all protein components isolated from the obliquely striated muscle, our in vitro experiments consistently show that SCBP may accelerate muscle relaxation similar as assumed for vertebrate parvalbumin.

Soluble calcium-binding proteins (SCBPs) of the earthworm Lumbricus terrestris: molecular characterization and localization by FISH in muscle and neuronal tissue

Soluble calcium-binding proteins (SCBPs) of invertebrates probably serve like their vertebrate counterpart-the parvalbumins-as soluble relaxing factors in muscles. Three SCBP isoforms (SCBP_1-3) have been isolated and biochemically characterized in the earthworm Lumbricus terrestris (Huch et al. in J Comp Physiol B 158:325-334, 1988). For SCBP₂, we found two isoforms named SCBP_2a/2b. Both of them together with SCBP₃ are present in the body wall muscle. In the gizzard solely, SCBP_2b and no SCBP_2a or SCBP₃ could be detected. The coding sequences of all three isoforms consist of 534 bp for 178 amino acids and contain four EF-hand motifs, of which the second EF-hands are truncated. Recombinant proteins show heat stability and a Ca²⁺-dependent mobility shift similar to the native proteins, indicating comparable calcium-binding properties. All three isoforms are encoded by three distinct and differentially expressed genes. The genes for SCBP_2a, SCBP_2b, and SCBP₃ are interrupted by only one intron, inserting at nearly the same positions. Northern blot analysis revealed two mRNA transcripts for SCBP₂ of approximately 1250 and 1500 kb and one transcript for SCBP₃ of approximately 1250 kb. SCBP mRNA was localized by fluorescent in situ hybridization in the body wall and the gizzard. The distribution of the staining intensities resembles that for the myosin ATPase activity and indicates a correlation between the amount of SCBP and speed of muscle contraction. In addition, SCBP mRNA was localized within the nervous tissue, the cerebral and subesophageal ganglia and the ventral nerve cord.

Toxicogenomic analysis provides new insights into molecular mechanisms of the sublethal toxicity of 2,4,6-trinitrotoluene in Eisenia fetida

Xenobiotics such as explosives and pesticides released into the environment can have lethal and sublethal impacts on soil organisms such as earthworms with potential subsequent impacts at highertrophic levels. To better understand the molecular toxicological mechanisms of 2,4,6-trinitrotoluene (TNT), a commonly used explosive, in Eisenia fetida, earthworms were exposed to a gradient of TNT-spiked soils for 28 days and impacts on gene expression were examined using a 4032 cDNA microarray. Reproduction was increased at low doses of TNT, whereas high doses of TNT reduced juvenile production. On the basis of reproduction responses to TNT, four treatments, that is, control, 2, 10.6, and 38.7 mg/kg, were selected for gene expression studies in a balanced interwoven loop design microarray experiment in which the expression of 311 transcripts was significantly affected. Reverse-transcription quantitative polymerase chain reaction (RT-QPCR) data on 68 selected differentially and nondifferentially expressed transcripts showed a significant correlation with microarray results. The expression of genes involved in multiple biological processes was altered, including muscle contraction, neuronal signaling and growth, ubiquitinylation, fibrinolysis and coagulation, iron and calcium homeostasis, oxygen transport, and immunity. Chitinase activity assays confirmed down-regulation of chitinase genes as indicated by array and RT-QPCR data. An acute toxicity test provided evidence that dermal contact with TNT can cause bleeding, inflammation, and constriction, which may be explained by gene expression results. Sublethal doses of TNT affected the nervous system, caused blood disorders similar to methemoglobinemia, and weakened immunity in E. fetida.

Invertebrate Muscles: Muscle Specific Genes and Proteins

This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.

Parvalbumin-immunoreactive proteins in the nervous system of planarians

1. Using immunological methods, we have identified parvalbumin-like material in the triclade flatworms, Polycelis nigra, Polycelis auriculata, Crenobia alpina, Dugesia tahitiensis, and Dugesia polychroa. 2. Western immunoblot analysis of these five species revealed heat stable parvalbumin-immunoreactive proteins between 32 kD and 44 kD. 3. Proteins at 19 and 32 kD revealed intense labeling with 45Ca2+. 4. Double immunodiffusion of planarian supernatants showed complete fusion of precipitates, indicating immunological relatedness of the parvalbumin-like material among the species investigated. 5. Immunocytochemical studies exhibit parvalbumin-immunoreactive material exclusively in neurons supporting the notion of an early evolutionary appearance of these proteins in the nervous system.

Sarcoplasmic calcium-binding protein

Sarcoplasmic calcium-binding proteins (SCPs) are members of the EF-hand calcium-binding protein family which are characterized by the presence of helix-loop-helix motifs in their amino acid sequence. SCPs have an M(r) of approximately 20,000, a pI of approximately 5 and interact with two to three calcium ions (Ca2+) with a KD of 10(-7) to 10(-8) M. Mg2+ ions antagonize Ca2+ ion binding in a complex manner so that these proteins are exquisitely fine-tuned to interfere with the Ca2+ signal. SCPs apparently fulfil no specific activatory function. They exhibit strong polymorphism, show a marked homology to coelenterate photoproteins (aequorin, luciferin) and have been found only in invertebrates, predominantly in muscle and neurons. In mollusks, SCPs are distributed in a tissue-specific manner, with immunoreactivity to SCP I-like isoforms localized in electrically silent neurons colocalized with serotonin, and immunoreactivity to SCP II-like isoforms exclusively present in muscle.

Sarcoplasmic calcium-binding proteins in Aplysia nerve and muscle cells

Muscle (body wall, buccal mass, heart) and neural tissue of the marine mollusc Aplysia californica was analysed for calcium-binding proteins using transblot/45Ca overlay, Western blotting and two-dimensional polyacrylamide gel electrophoresis, and several low molecular weight calcium-binding proteins were identified. Our results that Aplysia muscle contains an abundant protein with a M(r) of approximately 20,000 with strong 45Ca(2+)-binding ability and cross-reactivity to antibodies against the sarcoplasmic calcium-binding protein isoform II (SCP II) from Amphioxus. Immunocytochemical studies revealed that isoforms of SCP are distributed in a tissue-specific manner, SCP II-like protein is exclusively present in muscle fibres closely associated with the contractile machinery, whereas the isoform I (SCP I-like protein) is exclusively present in a subset of neurons, suggesting a function in their calcium regulation. In addition, a novel 45Ca(2+)-binding protein of M(r) 43,000, pl 4.7, was found in muscle and in neurons. A third protein of M(r) 40,000, pl 4.8, cross-reacts with anti-parvalbumin and anti-calbindin D-28K antibodies.

Sarcoplasmic calcium-binding protein-immunoreactive material in the central nervous system of the snail, Helix pomatia

In Helix pomatia a 10 kDa sarcoplasmic calcium binding protein I (SCP I)-immunoreactive material was localized immunologically in neurons of the central nervous system, including the electrically silent serotonergic metacerebral giant neuron. Antisera against sarcoplasmic calcium binding protein II (SCP II) stained a 20 kDa protein in individual muscle cells of the epineurium. SCP- and parvalbumin (PV)-immunoreactive material were not co-localized.

A soluble calcium-binding protein (SCBP) present in Drosophila melanogaster and Calliphora erythrocephala muscle cells

1. Soluble calcium binding proteins (SCBP) were isolated from homogenates of whole flies, from the thorax and from muscles of Drosophila melanogaster and Calliphora erythrocephala. 2. Crude preparations were obtained by extraction at low ionic strength, acid and heat treatment. The Drosophila protein was purified by gel filtration, hydrophobic interaction and ion exchange chromatography. In contrast to calmodulin the Drosophila SCBP did not bind to phenyl-Sepharose in a Ca(2+)-dependent way. 3. Both the Drosophila and the Calliphora protein revealed identical properties. 4. The apparent molecular mass of the SCBP is 24 kDa. Separation in urea-PAGE demonstrated the existence of two isoforms. 5. The calcium-binding property was assured by a calcium dependent electrophoretic mobility shift and autoradiography of 45Ca(2+)-incubated Western blots. 6. The proteins are abundant in the thorax and were even detectable in crude extracts of various muscles (leg muscles and the extracoxal depressor). In contrast, in power muscles and in the thoracic ganglion the proteins could not be observed.

Parvalbumin in the cardiac muscle of normal and haemoglobin-myoglobin-free antarctic fish

Three parvalbumin isotypes were isolated from the white muscle of haemoglobin-myoglobin-free antarctic fish Channichthys rhinoceratus. Antibodies against the parvalbumin mixture were raised in rabbits and used for discovery, quantitation and isolation by affinity chromatography of parvalbumin in the cardiac muscle of three antarctic fish species: Channichthys rhinoceratus, Champsocephalus gunnari and Notothenia neglecta. The cardiac muscle of these species contains parvalbumin in concentration close to 1 mumol per kg wet weight.