Biomedical subjects

Gábor Papp

Publications and source records attributed to Gábor Papp.

3 recordsLinked to original sources

PubMed2006

Conformational changes in actin filaments induced by formin binding to the barbed end.

Formins bind actin filaments and play an essential role in the regulation of the actin cytoskeleton. In this work we describe details of the formin-induced conformational changes in actin filaments by fluorescence-lifetime and anisotropy-decay experiments. The results show that the binding of the formin homology 2 domain of a mammalian formin (mouse mDia1) to actin filaments resulted in a less rigid protein structure in the microenvironment of the Cys374 of actin, weakening of the interactions between neighboring actin protomers, and greater overall flexibility of the actin filaments. The formin effect is smaller at greater ionic strength. The results show that formin binding to the barbed end of actin filaments is responsible for the increase of flexibility of actin filaments. One formin dimer can affect the dynamic properties of an entire filament. Analyses of the results obtained at various formin/actin concentration ratios indicate that at least 160 actin protomers are affected by the binding of a single formin dimer to the barbed end of a filament.

Actin Cytoskeleton↗

PubMed2006

Formins regulate actin filament flexibility through long range allosteric interactions.

The members of the formin family nucleate actin polymerization and play essential roles in the regulation of the actin cytoskeleton during a wide range of cellular and developmental processes. In the present work, we describe the effects of mDia1-FH2 on the conformation of actin filaments by using a temperature-dependent fluorescence resonance energy transfer method. Our results revealed that actin filaments were more flexible in the presence than in the absence of formin. The effect strongly depends on the mDia1-FH2 concentration in a way that indicates that more than one mechanism is responsible for the formin effect. In accordance with the more flexible filament structure, the thermal stability of actin decreased and the rate of phosphate dissociation from actin filaments increased in the presence of formin. The interpretation of the results supports a model in which formin binding to barbed ends makes filaments more flexible through long range allosteric interactions, whereas binding of formin to the sides of the filaments stabilizes the protomer-protomer interactions. These results suggest that formins can regulate the conformation of actin filaments and may thus also modulate the affinity of actin-binding proteins to filaments nucleated/capped by formins.

Actin Cytoskeleton↗

PubMed2002

[Bile duct obstruction caused by neurofibroma in a patient with Recklinghausen's disease].

INTRODUCTION: Neurofibromatosis type-I (von Recklinghausen's disease) is characterised by multiple cutan neurofibromas, cafe-au-lait spots, bone abnormalities and tumours of central and peripheral nerves. Gastrointestinal involvement occurs in 25 percent of all cases. CASE REPORT: The authors report a case of a 53-year-old man presenting with rare hepatobiliary complication. He complained of abdominal pain and he looked jaundiced. The abdominal ultrasound revealed cholestasis confirmed by the laboratory results. The endoscopic retrograd cholangiography showed nearly total obstruction in the middle part of common bile duct. Subsequently laparotomy and choledochoenterostomy was performed. Plexiform neurofibroma was found in the wall of common bile duct and several gastrointestinal stromal tumour seedings were identified on the serosal surface of the small intestine. Post surgery he remained symptom free and showed no sign of jaundice. CONCLUSION: The authors would like to draw attention to this extremely rare case, since only two similar cases appeared in the literature.

Cholangiopancreatography, Endoscopic Retrograde↗