Biomedical subjects

Anna Chorzalska

Publications and source records attributed to Anna Chorzalska.

4 recordsLinked to original sources

PubMed2006

Spectrin-phospholipid interactions. Existence of multiple kinds of binding sites?

The object of this paper is to review briefly the studies on the interactions of erythroid and non-erythroid spectrins with lipids in model and natural membranes. An important progress on the identification of lipid-binding sites has recently been made although many questions remain still unanswered. In particular, our understanding of the physiological role of such interactions is still limited. Another important issue is the occurrence of spectrins in membrane rafts, how they are attached to the raft and what is their function in rafts.

Binding Sites↗

PubMed2004

Mapping of an ankyrin-sensitive, phosphatidylethanolamine/phosphatidylcholine mono- and bi-layer binding site in erythroid beta-spectrin.

It has been shown previously that binding of vesicles and monolayers containing PE (phosphatidylethanolamine) by either erythroid or non-erythroid spectrin proved sensitive to inhibition by purified erythrocyte ankyrin. We tested the lipid-binding affinities of the purified ankyrin-binding domain of beta-spectrin and of its truncated mutants in four ways, by analysing: (1) penetration of 'loose' PE/PC (phosphatidylcholine) monolayers; (2) binding to liposomes in suspension; (3) competition with spectrin for liposomes; and (4) binding of a PE/PC monolayer in a surface plasmon resonance system. The results obtained indicated that the full-length ankyrin-binding domain bound PE/PC mono- and bi-layers with moderate affinity, penetrated monolayers and competed with spectrin for liposomes. Moreover, its truncated mutants that retained the N-terminal part, in contrast with those lacking eight or 38 N-terminal residues (which bound lipid mono- and bi-layers with lower affinity), bound PE/PC mono- and bi-layers with an affinity and capacity comparable with those of the full-length ankyrin-binding domain, and this activity was inhibited by purified erythrocyte ankyrin. The full-length domain, in contrast with the mutant lacking 38 N-terminal residues, induced a small increase in the fluidity of PE/PC membranes when probed with 5'-doxyl stearate, similar to the effect of purified spectrin. Therefore we conclude that the binding site for PE-rich lipids, which is sensitive to ankyrin inhibition, is located in a 38-residue N-terminal fragment of the beta-spectrin ankyrin-binding domain, and that the first eight residues play a key role in this activity.

Alternative Splicing↗

PubMed2003

The kinetics of haemolysis of spherocytic erythrocytes.

Spherocytosis is a hereditary disease. It results from mutations in genes that encode proteins participating in the attachment of the membrane skeleton to the plasma membrane bilayer of the erythrocyte. In affected cells, interaction between the spectrin-actin meshwork and integral membrane proteins is altered. This results in the weakening of plasma membrane mechanical resistance and diminishing its elasticity. Since defective cells are prone to mechanical destruction and phagocytosis in the spleen, the fraction of morphologically-altered erythrocytes is rather small; this in turn means such an examination is prone to errors. In this paper, we describe a simple method which could be useful in the identification of red blood cells with altered osmotic properties. The method is based on the measurement of the amount of light scattered by a suspension of the red blood cells, during which cells are exposed to osmotic stress in the stopped-flow regime. The obtained plots are fitted to a mathematical formula, the parameters of which can be used as quantitative indicators of the changes in red blood cells' osmotic features. Two types of spherocytotic samples were examined: those with a proven deficiency in ankyrin and those with a decrease in the band 3 anion transporting protein. The presented data show that this method gives a reliable indication of altered osmotic properties of the spherocytic cells.

Anion Exchange Protein 1, Erythrocyte↗

PubMedDate not supplied

Mitoxantrone changes spectrin-aminophospholipid interactions.

Understanding drug-membrane and drug-membrane protein interactions would be a crucial step towards understanding the action and biological properties of anthracyclines, as the cell membrane with its integral and peripheral proteins is the first barrier encountered by these drugs. In this paper, we briefly describe mitoxantrone-monolayer and mitoxantrone-bilayer interactions, focusing on the effect of mitoxantrone on the interactions between erythroid or nonerythroid spectrin with phosphatidylethanolamine-enriched mono- and bilayers. We found that mitoxantrone markedly modifies the interaction of erythroid and nonerythroid spectrins with phosphatidylethanolamine/phosphatidylcholine (PE/PC) monolayers. The change in delta pi induced by spectrins is several-fold larger in the presence of 72 nM mitoxantrone than in its absence: spectrin/mitoxantrone complexes induced a strong compression of the monolayer. Spin-labelling experiments showed that spectrin/mitoxantrone complexes caused significant changes in the order parameter measured using a 5'-doxyl stearate probe in the bilayer, but they practically did not affect the mobility of 16'-doxyl stearate. These results indicate close-to-surface interactions/penetrations without significant effect on the mid-region of the hydrophobic core of the bilayer. The obtained apparent equilibrium dissociation constants indicated relatively similar mitoxantrone-phospholipid and mitoxantrone-spectrin (erythroid and nonerythroid) binding affinities. These results might in part, explain the effect of mitoxantrone on spectrin distribution in the living cells.

Animals↗