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Nakakoshi M, Nishioka H, Katayama E. New versatile staining reagents for biological transmission electron microscopy that substitute for uranyl acetate. JOURNAL OF ELECTRON MICROSCOPY 2011; 60:401-7. [PMID: 22146677 DOI: 10.1093/jmicro/dfr084] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Aqueous uranyl acetate has been extensively used as a superb staining reagent for transmission electron microscopy of biological materials. However, recent regulation of nuclear fuel material severely restricts its use even for purely scientific purposes. Since uranyl salts are hazardous due to biological toxicity and remaining radioactivity, development of safe and non-radioactive substitutes is greatly anticipated. We examined two lanthanide salts, samarium triacetate and gadolinium triacetate, and found that 1-10% solution of these reagents was safe but still possess excellent capability for staining thin sections of plastic-embedded materials of animal and plant origin. Although post-fixation with osmium tetroxide was essential for high-contrast staining, post-staining with lead citrate could be eliminated if a slow-scan CCD camera is available for observation. These lanthanide salts can also be utilized as good negative-staining reagents to study supramolecular architecture of biological macromolecules. They were not as effective as a fixative of protein assembly, reflecting the non-hazardous nature of the reagents.
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Affiliation(s)
- Masamichi Nakakoshi
- Division of Biomolecular Imaging, Institute of Medical Science, University of Tokyo, 4-6-1, Shirokanedai Minato-ku, Tokyo 108-8639, Japan
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2
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Shishido H, Nakazato K, Katayama E, Chaen S, Maruta S. Kinesin-Calmodulin fusion protein as a molecular shuttle. J Biochem 2009; 147:213-23. [DOI: 10.1093/jb/mvp173] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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3
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Wang CLA. Caldesmon and the regulation of cytoskeletal functions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 644:250-72. [PMID: 19209827 DOI: 10.1007/978-0-387-85766-4_19] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Caldesmon (CaD) is an extraordinary actin-binding protein, because in addition to actin, it also bindsmyosin, calmodulin and tropomyosin. As a component of the smoothmuscle and nonmuscle contractile apparatus CaD inhibits the actomyosin ATPase activity and its inhibitory action is modulated by both Ca2+ and phosphorylation. The multiplicity of binding partners and diverse biochemical properties suggest CaD is a potent and versatile regulatory protein both in contractility and cell motility. However, after decades ofinvestigation in numerous laboratories, hard evidence is still lacking to unequivocally identify its in vivo functions, although indirect evidence is mounting to support an important role in connection with the actin cytoskeleton. This chapter reviews the highlights of the past findings and summarizes the current views on this protein, with emphasis of its interaction with tropomyosin.
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Affiliation(s)
- C L Albert Wang
- Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA.
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4
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Kudryashov DS, Vorotnikov AV, Dudnakova TV, Stepanova OV, Lukas TJ, Sellers JR, Watterson DM, Shirinsky VP. Smooth muscle myosin filament assembly under control of a kinase-related protein (KRP) and caldesmon. J Muscle Res Cell Motil 2003; 23:341-51. [PMID: 12630709 DOI: 10.1023/a:1022086228770] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Kinase-related protein (KRP) and caldesmon are abundant myosin-binding proteins of smooth muscle. KRP induces the assembly of unphosphorylated smooth muscle myosin filaments in the presence of ATP by promoting the unfolded state of myosin. Based upon electron microscopy data, it was suggested that caldesmon also possessed a KRP-like activity (Katayama et al., 1995, J Biol Chem 270: 3919-3925). However, the nature of its activity remains obscure since caldesmon does not affect the equilibrium between the folded and unfolded state of myosin. Therefore, to gain some insight into this problem we compared the effects of KRP and caldesmon, separately, and together on myosin filaments using turbidity measurements, protein sedimentation and electron microscopy. Turbidity assays demonstrated that KRP reduced myosin filament aggregation, while caldesmon had no effect. Additionally, neither caldesmon nor its N-terminal myosin binding domain (N152) induced myosin polymerization at subthreshold Mg2+ concentrations in the presence of ATP, whereas the filament promoting action of KRP was enhanced by Mg2+. Moreover, the amino-terminal myosin binding fragment of caldesmon, like the whole protein, antagonizes Mg(2+)-induced myosin filament formation. In electron microscopy experiments, caldesmon shortened myosin filaments in the presence of Mg2+ and KRP, but N152 failed to change their appearance from control. Therefore, the primary distinction between caldesmon and KRP appears to be that caldesmon interacts with myosin to limit filament extension, while KRP induces filament propagation into defined polymers. Transfection of tagged-KRP into fibroblasts and overlay of fibroblast cytoskeletons with Cy3KRP demonstrated that KRP colocalizes with myosin structures in vivo. We propose a new model that through their independent binding to myosin and differential effects on myosin dynamics, caldesmon and KRP can, in concert, control the length and polymerization state of myosin filaments.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Adenosine Triphosphate/pharmacology
- Animals
- Calcium-Binding Proteins/drug effects
- Calcium-Binding Proteins/genetics
- Calcium-Binding Proteins/metabolism
- Calmodulin-Binding Proteins/drug effects
- Calmodulin-Binding Proteins/metabolism
- Cells, Cultured
- Chick Embryo
- Chickens
- Kinesins
- Magnesium/metabolism
- Magnesium/pharmacology
- Microscopy, Electron
- Models, Biological
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle Proteins/drug effects
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Muscle, Smooth/ultrastructure
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/ultrastructure
- Myosins/drug effects
- Myosins/metabolism
- Myosins/ultrastructure
- Polymers/metabolism
- Protein Binding/drug effects
- Protein Binding/genetics
- Protein Structure, Tertiary/physiology
- Transfection
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Affiliation(s)
- Dmitry S Kudryashov
- Laboratory of Cell Motility, Cardiology Research Center, 3rd Cherepkovskaya Street 15A, Moscow 121552, Russia
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5
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Tominaga M, Kojima H, Yokota E, Orii H, Nakamori R, Katayama E, Anson M, Shimmen T, Oiwa K. Higher plant myosin XI moves processively on actin with 35 nm steps at high velocity. EMBO J 2003; 22:1263-72. [PMID: 12628919 PMCID: PMC151065 DOI: 10.1093/emboj/cdg130] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2002] [Revised: 01/21/2003] [Accepted: 01/27/2003] [Indexed: 11/12/2022] Open
Abstract
High velocity cytoplasmic streaming is found in various plant cells from algae to angiosperms. We characterized mechanical and enzymatic properties of a higher plant myosin purified from tobacco bright yellow-2 cells, responsible for cytoplasmic streaming, having a 175 kDa heavy chain and calmodulin light chains. Sequence analysis shows it to be a class XI myosin and a dimer with six IQ motifs in the light chain-binding domains of each heavy chain. Electron microscopy confirmed these predictions. We measured its ATPase characteristics, in vitro motility and, using optical trap nanometry, forces and movement developed by individual myosin XI molecules. Single myosin XI molecules move processively along actin with 35 nm steps at 7 micro m/s, the fastest known processive motion. Processivity was confirmed by actin landing rate assays. Mean maximal force was approximately 0.5 pN, smaller than for myosin IIs. Dwell time analysis of beads carrying single myosin XI molecules fitted the ATPase kinetics, with ADP release being rate limiting. These results indicate that myosin XI is highly specialized for generation of fast processive movement with concomitantly low forces.
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Affiliation(s)
| | | | - Etsuo Yokota
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe 651-2492,
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo 678-1297, Division of Biomolecular Imaging, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012 Japan and Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Corresponding author e-mail:
| | - Hidefumi Orii
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe 651-2492,
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo 678-1297, Division of Biomolecular Imaging, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012 Japan and Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Corresponding author e-mail:
| | | | - Eisaku Katayama
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe 651-2492,
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo 678-1297, Division of Biomolecular Imaging, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012 Japan and Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Corresponding author e-mail:
| | - Michael Anson
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe 651-2492,
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo 678-1297, Division of Biomolecular Imaging, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012 Japan and Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Corresponding author e-mail:
| | - Teruo Shimmen
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe 651-2492,
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo 678-1297, Division of Biomolecular Imaging, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012 Japan and Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Corresponding author e-mail:
| | - Kazuhiro Oiwa
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe 651-2492,
Department of Life Science, Graduate School and Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo 678-1297, Division of Biomolecular Imaging, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012 Japan and Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Corresponding author e-mail:
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6
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Fukuda M, Katayama E, Mikoshiba K. The calcium-binding loops of the tandem C2 domains of synaptotagmin VII cooperatively mediate calcium-dependent oligomerization. J Biol Chem 2002; 277:29315-20. [PMID: 12034723 DOI: 10.1074/jbc.m201697200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synaptotagmin VII (Syt VII), a proposed regulator for Ca2+-dependent exocytosis, showed a robust Ca2+-dependent oligomerization property via its two C2 domains (Fukuda, M., and Mikoshiba, K. (2001) J. Biol. Chem. 276, 27670-27676), but little is known about its structure or the critical residues directly involved in the oligomerization interface. In this study, site-directed mutagenesis and chimeric analysis between Syt I and Syt VII showed that three Asp residues in Ca2+-binding loop 1 or 3 (Asp-172, Asp-303, and Asp-357) are crucial to robust Ca(2+)-dependent oligomerization. Unlike Syt I, however, the polybasic sequence in the beta4 strands of the C2 structures (so-called "C2 effector domain") is not involved in the Ca2+-dependent oligomerization of Syt VII. The results also showed that the Ca2+-binding loops of the two C2 domains cooperatively mediate Syt VII oligomerization (i.e. the presence of redundant Ca2+-binding site(s)) as well as the importance of Ca2+-dependent oligomerization of Syt VII in Ca2+-regulated secretion. Expression of wild-type tandem C2 domains of Syt VII in PC12 cells inhibited Ca2+-dependent neuropeptide Y release, whereas mutant fragments lacking Ca2+-dependent oligomerization activity had no effect. Finally, rotary-shadowing electron microscopy showed that the Ca2+-dependent oligomer of Syt VII is "a large linear structure," not an irregular aggregate. By contrast, in the absence of Ca2+ Syt VII molecules were observed to form a globular structure. Based on these results, we suggest that the linear Ca2+-dependent oligomer may be aligned at the fusion site between vesicles and plasma membrane and modulate Ca2+-regulated exocytosis by opening or dilating fusion pores.
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Affiliation(s)
- Mitsunori Fukuda
- Fukuda Initiative Research Unit, RIKEN (the Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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7
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Mabuchi K, Li Y, Carlos A, Wang CL, Graceffa P. Caldesmon exhibits a clustered distribution along individual chicken gizzard native thin filaments. J Muscle Res Cell Motil 2002; 22:77-90. [PMID: 11563552 DOI: 10.1023/a:1010392322503] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Our earlier immuno-gold electron microscopic study indicated that the distribution of caldesmon (CaD) on actin filaments is not uniform and is restricted to the vicinity of the myosin filaments (Mabuchi K, Li Y, Tao T, Wang CLA (1996) J Muscle Res Cell Motil 17: 243). This suggested that CaD could effectively inhibit muscle contraction, if those actin filaments in the vicinity of myosin filaments were saturated with CaD. In the present study we further examined the distribution of CaD along isolated, crude and purified native thin filaments (NTF). Individual CaD molecules on purified NTF were visualized with the aid of a chemical crosslinker, 5,5'-dithiobis(2-nitrobenzoic acid), which efficiently crosslinks CaD to actin (Graceffa P, Adam LP, Lehman W (1993) Biochem J294: 63), and of a monoclonal anti-CaD antibody. The results indicated that individual NTF had alternating CaD-rich and CaD-deficient regions. Moreover, we found that the N-termini of all CaD molecules in a given cluster appeared on the same side of an actin filament. Electron microscopic images of crude NTF immunoprecipitated by a polyclonal antibody clearly indicated that the spacing between the CaD clusters is wide enough for myosin heads to interact with actin subunits. Similar clustering of CaD was also observed in plastic embedded tissue sections. These observations raise the possibility that CaD is not acting as a simple on/off switch, but more likely as a modulator, of smooth muscle contraction.
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Affiliation(s)
- K Mabuchi
- Muscle and Motility Group, Boston Biomedical Research Institute, Watertown, MA 02472, USA
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8
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Frisbie SM, Reedy MC, Yu LC, Brenner B, Chalovich JM, Kraft T. Sarcomeric binding pattern of exogenously added intact caldesmon and its C-terminal 20-kDa fragment in skinned fibers of skeletal muscle. J Muscle Res Cell Motil 1999; 20:291-303. [PMID: 10471992 DOI: 10.1023/a:1005490405222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Intact caldesmon and particularly the actin-binding C-terminal fragment (20-kDa) of caldesmon have been shown in skeletal muscle fibers to selectively displace low affinity, weakly bound cross-bridges from actin without significantly altering the actin attachment of force producing, strong binding cross-bridges (Brenner et al., 1991; Kraft et al., 1995a). However, the sarcomeric distribution and the specific binding of externally added caldesmon to the myofilaments of skeletal muscle fibers was not known. It was e.g., unclear whether caldesmon binds along actin in a manner similar to tropomyosin or whether it also binds to myosin. In this study, we determined the binding pattern of exogenously added intact caldesmon and its C-terminal 20-kDa fragment, respectively, in MgATP-relaxed rabbit skeletal muscle fibers using electron (EM) and confocal fluorescence microscopy (CFM). EM showed that similar to what has been demonstrated earlier for smooth muscle thin filaments (Lehman et al., 1989), intact caldesmon binds periodically every 38 nm along the thin filaments. CFM revealed that rhodamine-labeled intact caldesmon and the 20-kDa caldesmon fragment bind along nearly the entire length of the thin filaments. A portion of the I-band near the Z-line appears unlabeled, both when equilibrated at normal and long sarcomere lengths. The width of the unlabeled region seems to depend on ionic strength. The 20-kDa C-terminal caldesmon fragment binds in essentially the same pattern as intact caldesmon. This indicates that the high fluorescence intensity in the overlap region seen with intact caldesmon does not depend on caldesmon binding to myosin. X-ray diffraction was used to monitor the effects of filament lattice. Intact caldesmon at > 0.3 mg/ml induced disorder in the myofilament lattice. No such disordering was observed, however, when fibers were equilibrated with up to 0.8 mg/ml of the 20-kDa caldesmon fragment.
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Affiliation(s)
- S M Frisbie
- National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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9
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Gunst SJ. Applicability of the sliding filament/crossbridge paradigm to smooth muscle. Rev Physiol Biochem Pharmacol 1999; 134:7-61. [PMID: 10087907 DOI: 10.1007/3-540-64753-8_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- S J Gunst
- Indiana University School of Medicine, USA
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10
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Arner A, Pfitzer G. Regulation of cross-bridge cycling by Ca2+ in smooth muscle. Rev Physiol Biochem Pharmacol 1999; 134:63-146. [PMID: 10087908 DOI: 10.1007/3-540-64753-8_3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- A Arner
- Department of Physiology and Neuroscience, Lund University, Sweden
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11
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Graceffa P. Arrangement of the COOH-terminal and NH2-terminal domains of caldesmon bound to actin. Biochemistry 1997; 36:3792-801. [PMID: 9092808 DOI: 10.1021/bi961652w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Smooth muscle caldesmon is a single polypeptide chain with its NH2- and COOH-terminal domains separated by a long alpha-helix. Caldesmon was labeled at either Cys-153 in the NH2 domain or Cys-580 in the COOH domain with a variety of fluorescence probes. Fluorescence intensity, peak position, and polarization of probes on Cys-580 were very sensitive to the binding to actin (with or without tropomyosin), whereas for probes on Cys-153, there was a lack of response, in reconstituted or native actin thin filaments. From fluorescence resonance energy transfer from donor labels on either caldesmon cysteine to acceptor labels on Cys-374 of actin, the distance between the donor and acceptor was estimated to be 27 A for the donor at Cys-580 and 65-80 A for the donor at Cys-153. These findings were the same for caldesmon prepared with or without heat treatment and with striated or smooth muscle actin. These results, together with previous knowledge that COOH-terminal fragments of caldesmon bind to actin whereas NH2-terminal fragments do not, indicate that, while the COOH domain of caldesmon is bound to actin, the NH2 domain is largely dissociated. Fluorescence quenching studies showed that actin binding to caldesmon greatly decreased the accessibility of probes at caldesmon Cys-580 to the quencher, whereas for probes at Cys-153, actin afforded much less, but significant, protection from quenching. Consequently, it appears that, although the NH2 domain is mostly dissociated, it spends some time in the vicinity of actin, through either a weak interaction with actin or collisions with actin and/or because of restricted flexibility which constrains the NH2 domain to be close to the actin filament. Since the NH2 domain of caldesmon binds to the neck region of myosin, a dissociated NH2 domain may account for caldesmon's ability to link myosin and actin filaments.
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Affiliation(s)
- P Graceffa
- Muscle Research Group, Boston Biomedical Research Institute, Massachusetts 02114, USA.
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12
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Czuryło EA, Hellweg T, Eimer W, Dabrowska R. The size and shape of caldesmon and its fragments in solution studied by dynamic light scattering and hydrodynamic model calculations. Biophys J 1997; 72:835-42. [PMID: 9017208 PMCID: PMC1185606 DOI: 10.1016/s0006-3495(97)78717-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The size and the shape of caldesmon as well as its 50-kDa central and 19-kDa C-terminal fragments were investigated by photon correlation spectroscopy. The hydrodynamic radii, which have been calculated from the experimentally obtained translational diffusion coefficients, are 9.8 nm, 6.0 nm, and 2.9 nm, respectively. Moreover, the experimental values for the translational diffusion coefficients are compared with results obtained from hydrodynamic model calculations. Detailed models for the structure of caldesmon in solution are derived. The contour length is about 64 nm for all of the models used for caldesmon.
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Affiliation(s)
- E A Czuryło
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland
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Zhuang S, Mabuchi K, Wang CA. Heat treatment could affect the biochemical properties of caldesmon. J Biol Chem 1996; 271:30242-8. [PMID: 8939977 DOI: 10.1074/jbc.271.47.30242] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Smooth muscle caldesmon (CaD) exhibits apparent heat stability. A widely used purification procedure of CaD involves extensive heat treatment (Bretscher, A. (1984) J. Biol. Chem. 259, 12873-12880). CaD thus purified co-sediments with actin, inhibits actomyosin ATPase activity, and interacts with Ca2+/calmodulin, similarly to the unheated protein. On the other hand, heat-treated CaD binds to actin filaments in a tether-like fashion, whereas lengthwise binding dominates in vivo (Mabuchi, K., Lin, J. J.-C., and Wang, C.-L. A. (1993) J. Muscle Res. Cell Motil. 14, 54-64), suggesting that differences do exist between heat-purified CaD and the native protein. We have isolated, without heat treatment, full-length recombinant chicken gizzard CaD overexpressed in insect cells (High-FiveTM) using a baculovirus expression system. We found that such unheated CaD interacts with calmodulin 10 times stronger than does the heated CaD; its inhibitory action on actomyosin ATPase is reversed by a much lesser amount of calmodulin. Moreover, electron microscopic examination indicated that actin binding at the N-terminal region is more frequent in the unheated CaD, resulting in more lengthwise binding. These findings point to the fact that CaD is not entirely heat-stable; the C-terminal CaM-binding regions and the N-terminal actin-binding region are possibly affected by heat treatment.
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Affiliation(s)
- S Zhuang
- Muscle Research Group, Boston Biomedical Research Institute, Boston, Massachusetts 02114, USA.
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14
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Hnath EJ, Wang CL, Huber PA, Marston SB, Phillips GN. Affinity and structure of complexes of tropomyosin and caldesmon domains. Biophys J 1996; 71:1920-33. [PMID: 8889167 PMCID: PMC1233659 DOI: 10.1016/s0006-3495(96)79391-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The interaction of caldesmon domains with tropomyosin has been studied using x-ray crystallography and an optical biosensor. Only whole caldesmon and the carboxyl-terminal domain of caldesmon (CaD-4, chicken gizzard residues 597-756) bound to tropomyosin with greater than millimolar affinity at 100 and 150 microM salt. Under these conditions the affinities of whole caldesmon and CaD-4 were both in the micromolar range. Data from the x-ray studies showed that whole caldesmon bound to tropomyosin in several places, with the region of tightest interaction being at tropomyosin residues 70-100 and/or 230-260. Studies with CaD-4 revealed that this region corresponded to the strong binding site seen with whole caldesmon. Weaker association of other regions of caldesmon to tropomyosin residues 180-210 and 5-50 was also observed. The results suggest that the carboxyl-terminus of caldesmon binds tightly to tropomyosin and that other regions of caldesmon may interact with tropomyosin tightly only when they are held close to tropomyosin by the carboxyl-terminal domain. Four models are presented to show the possible interactions of caldesmon with tropomyosin.
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Affiliation(s)
- E J Hnath
- Department of Biochemistry and Cell Biology, W.M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005, USA
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15
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Gerthoffer WT, Yamboliev IA, Shearer M, Pohl J, Haynes R, Dang S, Sato K, Sellers JR. Activation of MAP kinases and phosphorylation of caldesmon in canine colonic smooth muscle. J Physiol 1996; 495 ( Pt 3):597-609. [PMID: 8887769 PMCID: PMC1160768 DOI: 10.1113/jphysiol.1996.sp021619] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. Phosphorylation of caldesmon was assayed in canine colonic circular smooth muscle strips labelled with 32P and stimulated with 10 microM acetylcholine. Caldesmon was isolated by two-dimensional non-equilibrium pH gel electrophoresis. Stimulation with acetylcholine increased caldesmon phosphorylation significantly from a basal level of 0.6 +/- 0.07 to 1.1 +/- 0.15 mol P1 (mol caldesmon)-1 after 2 min. 2. MAP kinase activities were measured in SDS extracts of muscle by a gel reconstitution method using myelin basic protein. Myelin basic protein kinase activities were observed at 38, 44, 50 and 57 kDa by the gel reconstitution method. Endogenous caldesmon kinase activities were also identified by the gel reconstitution method at 38, 44 and 50 kDa. The 38 and 44 kDa kinases comigrated with proteins labelled by anti-ERK1 MAP kinase antibodies on Western blots. Both 38 and 44 kDa MBP kinase activities increased significantly during contractions induced by 10 microM acetylcholine, 0.1 microM neurokinin A and 70 mM potassium. 3. Phorbol dibutyrate (0.1 microM) potentiated activation of MAP kinases and contraction of depolarized muscles while producing a decrease in fura-2 fluorescence ratio. This suggests that protein kinase C activation is coupled to MAP kinase activity in colonic smooth muscle. 4. MAP kinases isolated form muscle homogenates by Mono Q chromatography were assayed using the specific MAP kinase substrate peptide APRTPGGRR. Stimulation of muscles for 2 min with 10 microM acetylcholine activated both ERK1 and ERK2 MAP kinase activities 2-fold. 5. To determine the effects of caldesmon phosphorylation by MAP kinase on the cross-bridge cycle, actin sliding velocity was measured with an in vitro motility assay. Unphosphorylated turkey gizzard caldesmon (3 microM) significantly reduced mean sliding velocity. Phosphorylation of caldesmon with sea star ERK1 MAP kinase reversed the inhibitory effect of caldesmon on sliding velocity. The results are consistent with a protein kinase cascade being activated by contractile agonists in gastrointestinal smooth muscle which activates ERK MAP kinases leading to phosphorylation of caldesmon. Phosphorylation of caldesmon in vivo may reverse inhibitory influences of caldesmon on cross-bridge cycling.
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Affiliation(s)
- W T Gerthoffer
- Department of Pharmacology, University of Nevada School of Medicine, Reno 89557-0046, USA.
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Dabrowska R, Hinssen H, Gałazkiewicz B, Nowak E. Modulation of gelsolin-induced actin-filament severing by caldesmon and tropomyosin and the effect of these proteins on the actin activation of myosin Mg(2+)-ATPase activity. Biochem J 1996; 315 ( Pt 3):753-9. [PMID: 8645154 PMCID: PMC1217271 DOI: 10.1042/bj3150753] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We have investigated the cumulative effects of three smooth-muscle actin-binding proteins, gelsolin, caldesmon and tropomyosin, on actin activation of myosin Mg(2+)-ATPase activity under low-ionic-strength conditions. A combination of tropomyosin (at a stoicheiometric ratio to actin) and gelsolin (at a molar ratio to actin of up to 1:100) showed essentially additive stimulatory effects that were counteracted by caldesmon. Suppression of the gelsolin-induced activation of the ATPase by caldesmon was higher in the presence of tropomyosin although it was not complete even at stoicheiometric amounts of both proteins to actin. Since activation of actin-activated ATPase activity of myosin by gelsolin is related to its severing action, it is concluded that caldesmon and tropomyosin cannot fully protect actin filaments against the severing activity of gelsolin. Direct analysis of the actin-severing activity of gelsolin by a fluorimetric assay using pyrene-labelled actin confirmed this conclusion. Tropomyosin and caldesmon in saturating amounts relative to actin inhibited the activity of gelsolin by between 21 and 40% and 25 and 48% respectively, depending on the molar ratio of gelsolin to actin. The inhibitory effect was increased with a combination of both (up to 67%) although it was evident that even under these conditions the actin filaments were not fully protected from being severed by gelsolin. These findings were corroborated by electron-microscopic investigation of actin filaments with or without tropomyosin and caldesmon after the addition of gelsolin.
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Affiliation(s)
- R Dabrowska
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland
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