Isolation of a renin-like enzyme from the leech Theromyzon tessulatum

Evidence for stanniocalcin and a related receptor in annelids

Stanniocalcin (STC) is a prime example of a hormone whose discovery in fish led to its subsequent discovery in mammals. STC is considered to be first and foremost a vertebrate polypeptide hormone with regulatory effects on ion transport, mitochondrial function and steroid hormone synthesis. The gene is widely expressed in both fishes and mammals, and the hormone can operate via both local and endocrine signaling pathways. In spite of the growing catalogue of vertebrate hormones and receptors with homologues in invertebrates, the notion that there might be an invertebrate STC homolog has received scant attention to date. In the present study, we have provided evidence for STC in annelid worms (freshwater leeches). Western blot analysis revealed the presence of two STC immunoreactive (STCir) proteins in leech tissue extracts of 100 and 193 kDa. These same extracts significantly lowered the rate of gill calcium transport upon injection into fish. Similarly, fish STC increased the rate of whole body calcium uptake when administered to leeches, and STC receptors of high affinity were identified on isolated leech plasma membranes. Two discrete populations of STC-positive cells were also identified in leeches using antibodies to fish STC and fish STC cRNA probes. One of the cell types was confined to the skin. The second cell type was confined to the coelomic cavity and identified as an adipose cell, which in leeches is a major repository of fat. Collectively, the data constitutes compelling evidence for the existence of STC-related proteins and receptors in annelids that share structural and functional similarities with those in vertebrates.

Structure, evolutionary conservation, and functions of angiotensin- and endothelin-converting enzymes

Angiotensin-converting enzyme, a member of the M2 metalloprotease family, and endothelin-converting enzyme, a member of the M13 family, are key components in the regulation of blood pressure and electrolyte balance in mammals. From this point of view, they serve as important drug targets. Recently, the involvement of these enzymes in the development of Alzheimer's disease was discovered. The existence of homologs of these enzymes in invertebrates indicates that these enzyme systems are highly conserved during evolution. Most invertebrates lack a closed circulatory system, which excludes the need for blood pressure regulators. Therefore, these organisms represent excellent targets for gaining new insights and revealing additional physiological roles of these important enzymes. This chapter reviews the structural and functional aspects of ACE and ECE and will particularly focus on these enzyme homologues in invertebrates.

Compensation mechanism in tumor cell migration: mesenchymal-amoeboid transition after blocking of pericellular proteolysis

Invasive tumor dissemination in vitro and in vivo involves the proteolytic degradation of ECM barriers. This process, however, is only incompletely attenuated by protease inhibitor-based treatment, suggesting the existence of migratory compensation strategies. In three-dimensional collagen matrices, spindle-shaped proteolytically potent HT-1080 fibrosarcoma and MDA-MB-231 carcinoma cells exhibited a constitutive mesenchymal-type movement including the coclustering of beta 1 integrins and MT1-matrix metalloproteinase (MMP) at fiber bindings sites and the generation of tube-like proteolytic degradation tracks. Near-total inhibition of MMPs, serine proteases, cathepsins, and other proteases, however, induced a conversion toward spherical morphology at near undiminished migration rates. Sustained protease-independent migration resulted from a flexible amoeba-like shape change, i.e., propulsive squeezing through preexisting matrix gaps and formation of constriction rings in the absence of matrix degradation, concomitant loss of clustered beta 1 integrins and MT1-MMP from fiber binding sites, and a diffuse cortical distribution of the actin cytoskeleton. Acquisition of protease-independent amoeboid dissemination was confirmed for HT-1080 cells injected into the mouse dermis monitored by intravital multiphoton microscopy. In conclusion, the transition from proteolytic mesenchymal toward nonproteolytic amoeboid movement highlights a supramolecular plasticity mechanism in cell migration and further represents a putative escape mechanism in tumor cell dissemination after abrogation of pericellular proteolysis.

Elements of angiotensin system are involved in leeches and mollusks immune response modulation

We present immunocytochemical, biochemical and cellular evidences for the presence of a renin-angiotensin system (RAS) in coelomocytes of invertebrates (leech, Theromyzon tessulatum and mollusk Mytilus edulis). Leech coelomocytes are immunoreactive to polyclonal antisera raised against the T. tessulatum angiotensin-converting enzyme (ACE) and leech brain angiotensin II (AII) and a commercial anti-AT1 receptor. Biochemically, renin, ACE- and AT1-like receptor were identified in the leech immune cells. We further demonstrate that leech AII (10(-6) M) alone does not initiate nitric oxide (NO) release in invertebrate immunocytes but does only after pre-exposing the cells to IL-1 (15.9+/-2.6 nM; P<0.005 vs. 1.1 nM when AII is added alone). Similar results were obtained with human leukocytes (14.5+/-2.7 nM; P<0.005 IL-1+AII vs. 0.9 nM when AII is added alone). Then, an immunocytochemical study performed at the structural and ultrastructural levels confirmed the presence in same immune cells all the molecules of the renin-angiotensin system (RAS) in leeches as epitopes to IL-1-like protein and IL-1-like receptor. This is the first report in invertebrates and of a co-action between cytokines like substances and neuropeptides in an immune process and the involvement of the RAS in modulation of the immune response.

The angiotensin system elements in invertebrates

In this review, the different components of the renin-angiotensin system (RAS) in invertebrates are discussed. This system is implicated in osmoregulation, reproduction, memory processes and immune system regulation. As the elements of this hormone-enzymatic system also exist in invertebrates, it appears that the RAS originated very early in evolution.

The neuroendocrine system of annelids

In vertebrates the neuroendocrine system is based on chemical signaling between neural and endocrine structures. Final outcomes may be realized via chemical messengers traveling through circulatory conduits to their specific target sites. This process may rely, in part, on neurosecretion of the signaling molecules. The complexity of this system can be readily visualized when one considers the way in which interactions among classical neurotransmitters, cytokines, growth factors, and neuroendocrine hormones, in combination with autocrine and paracrine communication, can regulate cells and tissues. Apart from the neuroendocrine system there is also neuroimmune communication, consisting of reciprocal signaling between neuroendocrine and immune cells, which use the same molecules to coordinate their activity. Thus, our concept of the neuroendocrine system is constantly growing, despite its complexity, but it may be simply summarized as allowing bidirectional communication between neural and endocrine structures over distances greater than that achieved by synaptic communication. In the light of this, I demonstrate in this review that annelids, which are considered "simple" animals, also possess a neuroendocrine system.

Mytilus edulis hemolymph contains pro-opiomelanocortin: LPS and morphine stimulate differential processing

Mytilus edulis hemolymph contains mammalian-like proopiomelanocortin (POMC). The 20 kDa protein was purified by high pressure gel permeation chromatography, anti-adrenocorticotropin (ACTH)-affinity column and reverse-phase HPLC. The amino acid sequence determination was by Edman degradation, enzymatic treatments and Western blot analysis. Of the six peptides found in this opioid precursor, methionine-enkephalin, gamma-melanocyte stimulating hormone (MSH), alpha-MSH and ACTH exhibited 100, 80, 85 and 74% sequence identity, respectively, with the mammalian counterparts. beta-Endorphin and gamma-LPH exhibited only 25 and 10% sequence identity. Dibasic amino acid residues were found at the C-terminus of MSH and ACTH, indicating cleavage sites. The alpha-MSH is flanked at the C-terminus by Gly-Lys-Lys, representing an amidation signal. ACTH and CLIP (80% sequence identity) are also C-terminally flanked by dibasic amino acid residues. Furthermore, morphine, in a dose-dependent manner, increased the hemolymph levels of alpha-MSH and ACTH (1-39) in a naloxone and phosphoramidon antagonizable manner, indicating a neutral endopeptidase (24.11; NEP) mediated cleavage. Lipopolysaccharide (10 microg/animal) stimulated the processing of ACTH (1-39) yielding ACTH (1-24) in a cleavage that is independent of NEP, but dependent on aspartyl proteases, demonstrating differential enzymatic cleavage of ACTH (1-39). Taken together, POMC is present in invertebrates and its processing can be altered depending on the signal.

Immunocytochemical distribution of angiotensin I-converting enzyme-like immunoreactivity in the brain and testis of insects

Angiotensin converting enzyme (ACE) is Zn2+ metallopeptidase which plays an important role in blood pressure homeostasis in mammals and other vertebrates. Homologues of ACE involved in the biosynthesis of mammalian peptide hormones have also been identified in the insects, Musca domestica, Drosophila melanogaster and Haematobia irritans exigua. In the pursuit of the biological role of insect ACE, this work focused on the tissue and cellular distribution of ACE in several insect species. The localisation of ACE in the central nervous system and reproductive tissues from a number of insect species suggests that ACE is of physiological importance in these tissues. By means of an antiserum to housefly ACE, we found that ACE-like immunoreactivity was abundantly present in the neuropil areas of the brain of all insects investigated, suggesting a role for ACE in the metabolic inactivation of peptide neurotransmitters. Especially in the fleshfly, Neobellieria bullata neuropile staining is abundant. In the cockroach Leucophaea maderae, immunoreactive staining was abundant in the neuronal perikarya as well as in the neuropilar regions. Staining in neurosecretory cells was also observed in the brains of the lepidopteran species, Bombyx mori and Mamestra brassica. The localisation of ACE in neurosecretory cells is consistent with the role as a processing hormone, involved in the generation of active peptide hormones. ACE was found to be co-localised with peptides of the FXPRLamide family in M. brassica and in B. mori, suggesting a role for the biosynthesis of these hormones. Finally, we found ACE-like immunoreactivity in the testis of Locusta migratoria, N. bullata and Leptinotarsa decemlineata, providing additional evidence for its important role in insect reproduction.

Structural characterization of osmoregulator peptides from the brain of the leech Theromyzon tessulatum: IPEPYVWD and IPEPYVWD-amide

Neurons immunoreactive to an antiserum (a-OT) directed specifically against the C-terminal part (prolyl-leucyl-glycinamide) of vertebrate oxytocin (OT) were detected in the brain of the leech Theromyzon tessulatum. With high pressure gel permeation chromatography followed by reversed-phase HPLC on brain extracts, evidence was given of the presence of three peptides (P1, P2, P3) immunoreactive to a-OT. Results of injection experiments in T. tessulatum and of titrations of each peptide at the different physiological stages of the animals which showed a peak in peptide P1 amount at stage 3B, indicated that P1 is the active OT-like peptide. Using three steps of reversed-phase HPLC, Edman degradation and electrospray mass spectrometry, two sequences for P1 (IPEPYVWD and IPEPYVWD-amide) were found. These peptides differ from peptides to the oxytocin/vasopressin family and are unique in the animal kingdom. Confirmation of their action on the hydric balance and their distribution in the CNS were presented.

Metabolism of angiotensins by head membranes of the leech Theromyzon tessulatum

Angiotensins (angiotensin I, angiotensin II, angiotensin II-amide) have been isolated in leeches and such peptides are involved in diuresis in these animals. To explore possible inactivation mechanisms of these peptides, angiotensins were incubated with head membranes of the leech T. tessulatum. Membranes derived from head parts of this leech are very rich in peptidases. They contain endopeptidase-24.11-like enzyme (NEP-like) associated with a battery of exopeptidase. The way that angiotensins are degraded by the combined attack of these membrane peptidases has been investigated. The contribution of individual peptidases was assessed by adding inhibitors (phosphoramidon, captopril and amastatin) to the membrane fractions, when they were incubated with the peptides. In the case of angiotensin I, the primary attack was performed by a combined action of the NEP-like and the ACE-like enzymes, followed by aminopeptidase attacks. Angiotensin II and III were hydrolyzed by NEP-like enzyme at the same Tyr-Ile bond, whereas the N-terminal arginine residue of angiotensin III was removed by an arginyl aminopeptidase. These results show that angiotensins are efficiently degraded by membranes and that NEP-like enzyme plays a key role in this process.

Biochemical properties of the angiotensin-converting-like enzyme from the leech Theromyzon tessulatum

This article reports the evidence and the biochemical properties of an angiotensin-converting (ACE)-like enzyme from head parts of the leech Theromyzon tessulatum. After solubilization from membranes with Triton X-114, the ACE-like enzyme was purified from the detergent-poor fraction. Four steps of purification including gel permeation and anion exchange chromatographies followed by a reversed-phase HPLC were needed. This poor glycosylated peptidyl dipeptidase (of ca. 120 kDa) hydrolyzes, at pH 8.4 and at 37 degrees C, the Phe8-His9 bond of angiotensin I with a high catalytic activity (i.e., K(m): 830 microM and Kcat/K(m): 153 s-1 mM-1). The hydrolysis of angiotensin I is inhibitable at 80% by captopril (IC50 = 175 nM) and lisinopril (IC50 = 35 nM). This activity is strictly dependent on the presence of NaCl and is increased by Zn2+. This zinc metallopeptidase also attacks peptides that have in their sequence either Gly-His, Gly-Phe, or Phe-His bond [e.g., enkephalins (Kcat/K(m): 12 s-1 mM-1) or bradykinin (Kcat/K(m): 2200 s-1 mM-1]. Taken together, these arguments are consistent with an ACE-like activity implicated in metabolism of angiotensins and bradykinin in leeches.