Interaction of smooth muscle calponin and desmin

Abstract

Interaction of smooth-muscle calponin and desmin was analyzed by means of ultracentrifugation, fluorescent spectroscopy and affinity chromatography. At low and intermediate ionic strength (30-50 mM NaCI) eaiponin is cosedimented with desmin with an apparent dissociation constant 3-15 IxM and stoichiometry of 1 calponin/4-6 desmin. Calmodulin decreases the quantity of calponin bound to desmin. Increase of ionic strength up to 150 mM weakens calponin-desmin interaction, but even at this ionic strength part of calponin remains bound to desmin. Calponin increases the rate and extent of fluorescence quenching induced by polymerization of 5-iodoacetamidofluorescein-labeled desmin. Affmity chromatography data indicate that desmin-binding sites are located in the N-terminal 22 kDa fragment of calponin. Since calponin interacts with desmin with an affinity comparable with that of, e.g., tropomyosin and myosin we suppose that calponin-desmin interaction may be important for cytoskeleton organization.

Association of Calponin with Desmin Intermediate Filaments

“…We found that at physiological ionic strengths, CP interacts with synthetic desmin IFs only weakly, so that it is not likely that CP is associated with IFs via direct binding. We noted that this is in agreement with Wang and Gusev (27), who reported that CP binds to IFs only at low ionic strengths. Instead, we found that CP binds strongly to tetrameric desmin and that the primary binding site is likely to be at one end of the IF polymerization subunit.…”

“…These in vitro studies clearly show that although it does not associate with IFs directly, CP is capable of forming a co-polymer with desmin in IFs. We noted that these findings are consistent with those of Wang and Gusev (27), who reported that CP binds to IFs only at low ionic strengths and that CP inhibits the rate of desmin polymerization in a solution of 50 mM NaCl and 5 mM MgCl 2 at pH 8.3.…”

3-D image reconstruction of reconstituted smooth muscle thin filaments containing calponin: Visualization of interactions between F-actin and Calponin

“…Such linkage also seems plausible in the cytoskeletal domain of smooth muscle, which contains cytoskeletal b-actin, intermediate ®la-ments, and probably most of the calponin (North et al, 1994a,b;Mabuchi et al, 1997). Recent studies suggest that calponin may indeed bind to intermediate ®laments as well as actin ®laments (Wang & Gusev, 1996;Mabuchi et al, 1997). If calponin is present in the contractile domain as well as the cytoskeletal domain North et al, 1994b), then calponin might equally act as an intracellular strut linking intermediate ®laments and contractile actin.…”

Functional Analysis of Rat Acidic Calponin.

“…33) Interaction of Recombinant Acidic Calponin with Basic Calponin-Related Components Basic calponin has been reported to interact with F-actin, microtubules, desmin filaments, tropomyosin, calmodulin, S100 and PS vesicles. [1][2][3][4][5][6][15][16][17][18][19][20][21][22][23][24]27,28) We examined whether the recombinant acidic calponin interacts with these proteins and PS vesicles using sedimentation and bead assays (Fig. 1).…”