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A Milzani

Publications and source records attributed to A Milzani.

33 records · Page 2Linked to original sources
PubMed1993

DXR depresses the alpha-actinin-induced formation of actin bundles.

The filament-to-filament interactions in cardiac alpha-actinin/F-actin mixtures were investigated in the presence of doxorubicin. Stoichiometrical concentrations of the drug in the assembly medium inhibit the growth of alpha-actinin/F-actin three-dimensional structures, as shown by low speed centrifugation, light scattering, A320nm, electron microscopy and low shear viscosity tests. DXR-induced short actin bundle formation could be related to the inhibition of the bundle elongation mechanism, and furthermore, could account for some morphological evidences in DXR-treated living cells. Our results support both the formation pathway of actin bundles as proposed by Stokes and DeRosier (1991), and the observations of Molinari et al. (1990) on the human CG5 cell line.

Actin Cytoskeleton↗
PubMed1992

Xenopus laevis sperm proteins, previously identified as surface proteins with egg coat binding capability, are indeed histone H4, histone H3, and sperm specific protein SP2.

Recently, four Xenopus sperm proteins thought to be involved in binding to the egg envelope were identified (Lindsay and Hedrick, J. Exp. Zool., 245:286-293, '88). We have studied the three more abundant ones of apparent molecular weight of 14, 19, and 25 kd in SDS-PAGE. We have shown that these proteins are indeed nuclear basic proteins: the 14 kd is the histone H4, the 19 kd is the histone H3, and the 25 kd is the sperm-specific protein SP2.

Amino Acid Sequence↗
PubMed1992

Interaction of cardiac alpha-actinin and actin in the presence of doxorubicin.

The therapeutic use of doxorubicin (an antitumoral antibiotic belonging to the anthracycline group) is limited by its cardiotoxicity. Adriamycin (DXR) causes myocardial subcellular damage, such as myocytolysis, disarray of actin filaments, and alterations in the Z-band with loss of sarcomeric organization. We studied the effect of stoichiometrical concentrations of DXR on the interaction between cardiac actin and alpha-actinin in solution. Doxorubicin inhibits the formation of alpha-actinin/actin tridimensional networks and bundles. The main effect of the drug seems to be on the size of the actin polymers.

Actin Cytoskeleton↗
PubMed1991

Effects of lithium ions on actin polymerization in the presence of magnesium ions.

In spite of the abundant literature, questions on the biological action of Li+ are far from being answered. In the present paper we demonstrate that modification of the salt composition of the medium for actin polymerization, by gradually replacing K+ with Li+, leads to a dose-related change in the time course of actin assembly. The presence of Li+ influences actin polymerization in vitro by enhancing nucleation and decreasing critical monomer concentration at steady state. Furthermore, Li+ stabilizes actin polymers mainly by lowering the absolute value of the dissociation rate constant (K-) and shifting (towards lower values of actin monomer concentrations) the range of G-actin concentrations in which filament-subunit flux can occur. The influence of Li+ on actin and tubulin polymerization in vitro suggests that cytoskeletal structures could be some of the cytoplasmic targets of this ion.

Actins↗
PubMed1991

Lithium increases actin polymerization rates by enhancing the nucleation step.

Lithium affects the polymerization mechanism of some cytoskeletal proteins in vitro, so its biological activity could also reflect lithium influence on assembly processes. Our data demonstrate that lithium nucleates actin polymerization and, in parallel, is less effective in the elongation step. Furthermore, falling-ball and fluorimetric tests suggested that lithium-induced actin polymers at steady-state are shorter than K(+)-polymerized actin filamentous structures. The lithium-induced actin assembly seems to follow the "reversible polymerization model" and the critical concentration of Li(+)-assembled actin at steady-state is markedly lower than that of sister actin samples polymerized by potassium chloride. Finally, the stabilization of actin nuclei induced by lithium ions could be related to their effect of lowering the dissociation rate constant.

Actin Cytoskeleton↗
PubMed1990

Metal ions modulate the effect of doxorubicin on actin assembly.

Doxorubicin (DXR) exhibits a significant activity in many human malignant neoplasms but, unfortunately, produces many undesirable cellular troubles which mainly lead to a severe dose-dependent cardiomyopathy. Many Authors had suggested that doxorubicin interacts with actin and affects the intracellular ion composition; following this reasoning, we studied the effect of doxorubicin on actin polymerization in vitro induced by different metal ions. In this paper we show that the negative action of doxorubicin on actin polymerization (inhibition of filament growth, reduction of polymer amount and polymer size at steady-state) is strongly ion-dependent. With this finding, we suggest that the direct action of antibiotic on actin assembly, in the presence of the drug-related changes in cytoplasmic electrolyte pattern, could become predominant in vivo.

Actin Cytoskeleton↗
PubMed1988

How does doxorubicin interfere with actin polymerization?

It is well known that doxorubicin (adriamycin), an antibiotic with an antitumoral action, has some undesirable side effects. Among these, the most serious is, undoubtedly, damage to myocardial tissue (progressive cardiomyopathy). We have for some time focused our attention on the effect of this drug on cellular contractile systems and, more specifically, on the process of actin polymerization, which we consider to be an extremely delicate key point for the economy of most cellular motor manifestations. In the present study, using capillary viscometry, spectrofluorometry and electron microscopy, we have shown a negative action of doxorubicin on various important chemical events which contribute to the transformation of G-actin into F-actin. Specifically, we found that the drug mainly acts by reducing the polymer size. A possible action mechanism of the antibiotic is proposed and a plausible correlation among the events described in vitro and those observed in vivo is advanced.

Actins↗
PubMed1988

Dose-dependence of doxorubicin effect on actin assembly in vitro.

Doxorubicin (Adriamycin), one of the most potent antibiotics used in tumor chemotherapy, shows many undesirable side effects. We studied the effect of different drug concentrations on the biochemistry of cell motility and, in particular, on potassium-induced actin polymerization. It is well known, in fact, that the actin aggregational status could dramatically influence many cell motility manifestations. Our results clearly show that stoichiometric and substoichiometric amounts of doxorubicin negatively influence actin polymerization by inhibiting both the filament growth and the polymer amount at steady-state; the balance between the two different effects seems to be in relation to the drug concentration. The obtained results could explain some of the doxorubicin effects previously observed in vivo.

Actins↗
PubMed1986

Computer-assisted mathematical analysis of sigmoid biological events.

A program in BASIC is described which allows accurate quantification of some numerical parameters that can be objectively correlated to biological indexes in sigmoid biological events. Attention was focused on the polymerization process of actin (a muscle protein with a mol. wt of 42,000 daltons) studied as the variation in the OD360 index with time. The experimental points, if plotted, can be well approximated by a rational function of the type delta OD360 = f(t), which passes through the origin and can be represented graphically by a sigmoid curve. The program was very helpful in comparing the experimental curves and in analysing significant parameters, such as maximum velocity and asymptote, that characterize these curves and whose interpretation would otherwise be purely subjective.

Actins↗
PubMed1984

Doxorubicin affects actin assembly in vitro.

In vitro experiments on actin polymerization in the presence of doxorubicin show that the rate of salt-induced actin assembly is negatively affected by the drug. The decreased amount of actin monomers keeping their ability to self-interact to give F actin (microfilaments) probably explains the reduction of assembly value. Drug action is dose-dependent and various discrepancies are explained by the limitations of the techniques used.

Actins↗
PubMedDate not supplied

S-glutathionylation: from redox regulation of protein functions to human diseases.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) play an integral role in the modulation of several physiological functions but can also be potentially destructive if produced in excessive amounts. Protein cysteinyl thiols appear especially sensitive to ROS/RNS attack. Experimental evidence started to accumulate recently, documenting that S-glutathionylation occurs in a number of physiologically relevant situations, where it can produce discrete modulatory effects on protein function. The increasing evidence of functional changes resulting from this modification, and the growing number of proteins shown to be S-glutathionylated both in vitro and in vivo support this contention, and confirm this as an attractive area of research. S-glutathionylated proteins are now actively investigated with reference to problems of biological interest and as possible biomarkers of human diseases associated with oxidative/nitrosative stress.

Disease↗
PubMedDate not supplied

Lithium preserves F-actin from the disarrangement induced by either DNase I or cytochalasin D.

Light scattering at 546 nm, which is mainly related to the presence of rodlike particles longer than 50 nm, showed that Li+ accelerates the formation of actin filaments. Intermolecular cross-linking with N,N'-1,4-phenylene-bismaleimide proved that the observed enhancement in the light-scattering intensity is caused by the increase in the concentration of actin oligomers, which gradually elongate to form longer filaments. DNase-I-related F-actin disassembly was reduced in the presence of lithium ions, as demonstrated by fluorimetric and viscometric experiments. Li(+)-F-actin showed an apparently similar behaviour when exposed to cytochalasin D. We confirm that Li+ acts on actin polymerization by stabilizing actin nuclei and polymers. The stabilization of cytoskeletal polymers really appears as one of the mechanisms by which lithium ions influence some of the cell activities.

Actins↗
PubMedDate not supplied

N-ethylmaleimide-modified actin filaments do not bundle in the presence of alpha-actinin.

We show that the modification of actin subdomain 1 by N-ethylmaleimide (NEM), which binds Cys-374 close to the C-terminus of the molecule, inhibits the alpha-actinin-induced bundling of actin filaments. This effect is not merely related to the block of Cys-374, since N-(1-pyrenyl)iodoacetamide (pyrene-IA) is unable to prevent bundling. Considering that NEM (but not pyrene-IA) influences actin assembly, we suggest that the inhibition of the actin-alpha-actinin interaction is due to the chemical modification of actin Cys-374 which, by inducing a marked spatial reorganization of actin monomers, is able to modify both the intra- and inter-molecular interactions of this protein. Finally, NEM-modified actin filaments form bundles in the presence of polyethylene glycol 6000 since, in this case, the side by side association of actin filaments does not depend on the accessibility of binding sites nor on the formation of chemical bonds.

Actin Cytoskeleton↗