1
|
Ydenberg CA, Johnston A, Weinstein J, Bellavance D, Jansen S, Goode BL. Combinatorial genetic analysis of a network of actin disassembly-promoting factors. Cytoskeleton (Hoboken) 2015; 72:349-61. [PMID: 26147656 PMCID: PMC5014199 DOI: 10.1002/cm.21231] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 06/29/2015] [Accepted: 07/01/2015] [Indexed: 12/12/2022]
Abstract
The patterning of actin cytoskeleton structures in vivo is a product of spatially and temporally regulated polymer assembly balanced by polymer disassembly. While in recent years our understanding of actin assembly mechanisms has grown immensely, our knowledge of actin disassembly machinery and mechanisms has remained comparatively sparse. Saccharomyces cerevisiae is an ideal system to tackle this problem, both because of its amenabilities to genetic manipulation and live‐cell imaging and because only a single gene encodes each of the core disassembly factors: cofilin (COF1), Srv2/CAP (SRV2), Aip1 (AIP1), GMF (GMF1/AIM7), coronin (CRN1), and twinfilin (TWF1). Among these six factors, only the functions of cofilin are essential and have been well defined. Here, we investigated the functions of the nonessential actin disassembly factors by performing genetic and live‐cell imaging analyses on a combinatorial set of isogenic single, double, triple, and quadruple mutants in S. cerevisiae. Our results show that each disassembly factor makes an important contribution to cell viability, actin organization, and endocytosis. Further, our data reveal new relationships among these factors, providing insights into how they work together to orchestrate actin turnover. Finally, we observe specific combinations of mutations that are lethal, e.g., srv2Δ aip1Δ and srv2Δ crn1Δ twf1Δ, demonstrating that while cofilin is essential, it is not sufficient in vivo, and that combinations of the other disassembly factors perform vital functions. © 2015 The Authors. Cytoskeleton Published by Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Casey A Ydenberg
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, 02454
| | - Adam Johnston
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, 02454
| | - Jaclyn Weinstein
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, 02454
| | - Danielle Bellavance
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, 02454
| | - Silvia Jansen
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, 02454
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, 02454
| |
Collapse
|
2
|
Jansen S, Collins A, Golden L, Sokolova O, Goode BL. Structure and mechanism of mouse cyclase-associated protein (CAP1) in regulating actin dynamics. J Biol Chem 2014; 289:30732-30742. [PMID: 25228691 DOI: 10.1074/jbc.m114.601765] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Srv2/CAP is a conserved actin-binding protein with important roles in driving cellular actin dynamics in diverse animal, fungal, and plant species. However, there have been conflicting reports about whether the activities of Srv2/CAP are conserved, particularly between yeast and mammalian homologs. Yeast Srv2 has two distinct functions in actin turnover: its hexameric N-terminal-half enhances cofilin-mediated severing of filaments, while its C-terminal-half catalyzes dissociation of cofilin from ADP-actin monomers and stimulates nucleotide exchange. Here, we dissected the structure and function of mouse CAP1 to better understand its mechanistic relationship to yeast Srv2. Although CAP1 has a shorter N-terminal oligomerization sequence compared with Srv2, we find that the N-terminal-half of CAP1 (N-CAP1) forms hexameric structures with six protrusions, similar to N-Srv2. Further, N-CAP1 autonomously binds to F-actin and decorates the sides and ends of filaments, altering F-actin structure and enhancing cofilin-mediated severing. These activities depend on conserved surface residues on the helical-folded domain. Moreover, N-CAP1 enhances yeast cofilin-mediated severing, and conversely, yeast N-Srv2 enhances human cofilin-mediated severing, highlighting the mechanistic conservation between yeast and mammals. Further, we demonstrate that the C-terminal actin-binding β-sheet domain of CAP1 is sufficient to catalyze nucleotide-exchange of ADP-actin monomers, while in the presence of cofilin this activity additionally requires the WH2 domain. Thus, the structures, activities, and mechanisms of mouse and yeast Srv2/CAP homologs are remarkably well conserved, suggesting that the same activities and mechanisms underlie many of the diverse actin-based functions ascribed to Srv2/CAP homologs in different organisms.
Collapse
Affiliation(s)
- Silvia Jansen
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454 and
| | - Agnieszka Collins
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454 and
| | - Leslie Golden
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454 and
| | - Olga Sokolova
- Faculty of Biology, Moscow State University, GSP-1, 1 Leninskie Gory, Building 12, 119991 Moscow, Russia
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454 and.
| |
Collapse
|
3
|
Affiliation(s)
- Beat Ludin
- Friedrich Miescher Institute, Basel, Switzerland
| | - Andrew Matus
- Friedrich Miescher Institute, Basel, Switzerland
| |
Collapse
|
4
|
Pontrello CG, Ethell IM. Accelerators, Brakes, and Gears of Actin Dynamics in Dendritic Spines. ACTA ACUST UNITED AC 2009; 3:67-86. [PMID: 20463852 DOI: 10.2174/1874082000903020067] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dendritic spines are actin-rich structures that accommodate the postsynaptic sites of most excitatory synapses in the brain. Although dendritic spines form and mature as synaptic connections develop, they remain plastic even in the adult brain, where they can rapidly grow, change, or collapse in response to normal physiological changes in synaptic activity that underlie learning and memory. Pathological stimuli can adversely affect dendritic spine shape and number, and this is seen in neurodegenerative disorders and some forms of mental retardation and autism as well. Many of the molecular signals that control these changes in dendritic spines act through the regulation of filamentous actin (F-actin), some through direct interaction with actin, and others via downstream effectors. For example, cortactin, cofilin, and gelsolin are actin-binding proteins that directly regulate actin dynamics in dendritic spines. Activities of these proteins are precisely regulated by intracellular signaling events that control their phosphorylation state and localization. In this review, we discuss how actin-regulating proteins maintain the balance between F-actin assembly and disassembly that is needed to stabilize mature dendritic spines, and how changes in their activities may lead to rapid remodeling of dendritic spines.
Collapse
Affiliation(s)
- Crystal G Pontrello
- Biomedical Sciences Division and Neuroscience program, University of California Riverside, USA
| | | |
Collapse
|
5
|
Yao W, Nathanson J, Lian I, Gage FH, Sung LA. Mouse erythrocyte tropomodulin in the brain reported by lacZ knocked-in downstream from the E1 promoter. Gene Expr Patterns 2007; 8:36-46. [PMID: 17920339 DOI: 10.1016/j.modgep.2007.08.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 07/19/2007] [Accepted: 08/22/2007] [Indexed: 01/14/2023]
Abstract
Erythrocyte tropomodulin (E-Tmod, Tmod1) is a tropomyosin-binding protein that caps the slow-growing end of actin filaments. In erythrocytes, it may favor the formation of short actin protofilaments needed for elastic cell deformation. Previously we created a knockout mouse model in which lacZ was knocked-in downstream of the E1 promoter to report the expression of full length E-Tmod. Here we utilize E-Tmod(+/lacZ) mice to study E-Tmod expression patterns in the CNS. X-gal staining and in situ hybridization of adults revealed its restricted expression in the olfactory bulb, hippocampus, cerebral cortex, basal ganglia, nuclei of brain stem and cerebellum. In neonates, signals in the cortex and caudate putamen increased from days 15 to 40. Immunohistochemistry also revealed that signals for beta-galactosidase coincided with that of NeuN, a post-mitotic nuclear marker for neurons, but not that for GFAP+ astrocytes or APC+ oligodendrocytes, suggesting E-Tmod/lacZ-positive cells in the CNS were neurons. Large neurons, e.g., mitral cells in olfactory bulb and mossy cells in hilus of the dentate gyrus are among those that expressed very high levels of E-Tmod in the CNS.
Collapse
Affiliation(s)
- Weijuan Yao
- Department of Bioengineering and Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093-0412, USA
| | | | | | | | | |
Collapse
|
6
|
Jonckheere V, Lambrechts A, Vandekerckhove J, Ampe C. Dimerization of profilin II upon binding the (GP5)3 peptide from VASP overcomes the inhibition of actin nucleation by profilin II and thymosin beta4. FEBS Lett 1999; 447:257-63. [PMID: 10214957 DOI: 10.1016/s0014-5793(99)00293-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Profilin II dimers bind the (GP5)3 peptide derived from VASP with an affinity of approximately 0.5 microM. The resulting profilin II-peptide complex overcomes the combined capacity of thymosin beta4 and profilin II to inhibit actin nucleation and restores the extent of filament formation. We do not observe such an effect when barbed filament ends are capped. Neither can profilin I, in the presence of the peptide, promote actin polymerization during its early phase consistent with a lower affinity. Since a Pro17 peptide-profilin II complex only partially restores actin polymerization, the glycine residues in the VASP peptide appear important.
Collapse
Affiliation(s)
- V Jonckheere
- Flanders Interuniversity Institute of Biotechnology, Department of Biochemistry, Faculty of Medicine, Universiteit Gent, Ghent, Belgium
| | | | | | | |
Collapse
|
7
|
Schlüter K, Schleicher M, Jockusch BM. Effects of single amino acid substitutions in the actin-binding site on the biological activity of bovine profilin I. J Cell Sci 1998; 111 ( Pt 22):3261-73. [PMID: 9788869 DOI: 10.1242/jcs.111.22.3261] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
For a detailed analysis of the profilin-actin interaction, we designed several point mutations in bovine profilin I by computer modeling. The recombinant proteins were analyzed in vitro for their actin-binding properties. Mutant proteins with a putatively higher affinity for actin were produced by attempting to introduce an additional bond to actin. However, these mutants displayed a lower affinity for actin than wild-type profilin, suggesting that additional putative bonds created this way cannot increase profilin's affinity for actin. In contrast, mutants designed to have a reduced affinity for actin by eliminating profilin-actin bonds displayed the desired properties in viscosity assays, while their binding sites for poly(L)proline were still intact. The profilin mutant F59A, with an affinity for actin reduced by one order of magnitude as compared to wild-type profilin, was analyzed further in cells. When microinjected into fibroblasts, F59A colocalized with the endogenous profilin and actin in ruffling areas, suggesting that profilins are targeted to and tethered at these sites by ligands other than actin. Profilin null cells of Dictyostelium were transfected with bovine wild-type profilin I and F59A. Bovine profilin I, although expressed to only approximately 10% of the endogenous profilin level determined for wild-type Dictyostelium, caused a substantial rescue of the defects observed in profilin null amoebae, as seen by measuring the growth of colony surface areas and the percentage of polynucleated cells. The mutant protein was much less effective. These results emphasize the highly conserved biological function of profilins with low sequence homology, and correlate specifically their actin-binding capacity with cell motility and proliferation.
Collapse
Affiliation(s)
- K Schlüter
- Cell Biology, Zoological Institute, Technical University of Braunschweig, D-38092 Braunschweig, Germany
| | | | | |
Collapse
|
8
|
Miki H, Takenawa T. Direct binding of the verprolin-homology domain in N-WASP to actin is essential for cytoskeletal reorganization. Biochem Biophys Res Commun 1998; 243:73-8. [PMID: 9473482 DOI: 10.1006/bbrc.1997.8064] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Verprolin is a yeast protein whose inactivation leads to a cytoskeletal defect characterized by the abnormal organization of actin filaments. Recently, two mammalian proteins previously shown to regulate the actin cytoskeleton, Wiskott-Aldrich Syndrome Protein (WASP) and its homolog expressed in neurons (N-WASP), were found to possess short peptide motifs homologous to one part of verprolin. However, the physiological function of the homologous regions (verprolin-homology domain, VPH domain) remains unknown. Here we report the importance of the VPH domain as the direct actin binding region. In the case of N-WASP, the VPH domain co-acts with the cofilinhomologous region to sever actin filaments in vitro. Furthermore, the VPH domain is indispensable for the reorganization of the actin cytoskeleton by N-WASP downstream of tyrosine kinases in living cells. All data demonstrate that the VPH domain plays critical roles in the regulation of the actin cytoskeleton.
Collapse
Affiliation(s)
- H Miki
- Department of Biochemistry, University of Tokyo, Japan
| | | |
Collapse
|
9
|
Schlüter K, Jockusch BM, Rothkegel M. Profilins as regulators of actin dynamics. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1359:97-109. [PMID: 9409807 DOI: 10.1016/s0167-4889(97)00100-6] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- K Schlüter
- Cell Biology, Zoological Institute, Technical University of Braunschweig, Germany
| | | | | |
Collapse
|
10
|
Hayakawa K, Ono S, Nagaoka R, Saitoh O, Obinata T. Differential assembly of cytoskeletal and sarcomeric actins in developing skeletal muscle cells in vitro. Zoolog Sci 1996; 13:509-17. [PMID: 8940906 DOI: 10.2108/zsj.13.509] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Monoclonal antibodies (McAb) to actin were prepared to analyze the assembly of actin isoforms in developing muscle cells in vitro. One of the antibodies (SkA-06) was specific for alpha-sarcomeric actin isoforms in skeletal and cardiac muscles, while the others recognized cytoskeletal (beta, gamma) actin isoforms in smooth muscle and non-muscle tissues as well as the sarcomeric (alpha) actins. Using SkA-06 and a polyclonal antibody (PcAb) specific for cytoskeletal actins, the subcellular localization of the actin isoforms was examined by immunocytochemical methods. While in developing young myotubes, cytoskeletal and sarcomeric actins were co-localized in nascent myofibrils or stress-fiber-like structures, sarcomeric actins predominated in striated myofibrils in more developed myotubes. When FITC-labeled cytoskeletal and sarcomeric actins were introduced into young myotubes by a microinjection method, the latter became detectable in striated structures sooner than the former but they were finally incorporated into striated myofibrils. These results suggest that alpha-actin(s) as well as beta- and gamma-actins can be incorporated into myofibrils, but alpha-actin(s) is assembled preferentially into myofibrils in developing muscle cells.
Collapse
Affiliation(s)
- K Hayakawa
- Department of Biology, Faculty of Science, Chiba University, Japan
| | | | | | | | | |
Collapse
|
11
|
Wang XH, Zheng JQ, Poo MM. Effects of cytochalasin treatment on short-term synaptic plasticity at developing neuromuscular junctions in frogs. J Physiol 1996; 491 ( Pt 1):187-95. [PMID: 9011610 PMCID: PMC1158769 DOI: 10.1113/jphysiol.1996.sp021206] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
1. The role of actin microfilaments in synaptic transmission was tested by monitoring spontaneous and evoked transmitter release from developing neuromuscular synapses in Xenopus nerve-muscle cultures, using whole-cell recording of synaptic currents in the absence and presence of microfilament-disrupting agents cytochalasins B and D. 2. Treatment with cytochalasins resulted in disruption of microfilament networks in the growth cone and the presynaptic nerve terminal of spinal neurons in Xenopus nerve-muscle cultures, as revealed by rhodamine-phalloidin staining. 3. The same cytochalasin treatment did not significantly affect the spontaneous or evoked synaptic currents during low-frequency stimulation at 0.05 Hz in these Xenopus cultures. Synaptic depression induced by high-frequency (5 Hz) stimulation, however, was reduced by this treatment. Paired-pulse facilitation for short interpulse intervals was also increased by the treatment. 4. These results indicate that disruption of microfilaments alters short-term changes in transmitter release induced by repetitive activity, without affecting normal synaptic transmission at low frequency. 5. Our results support the notion that actin microfilaments impose a barrier for mobilization of synaptic vesicles from the reserve pool, but do not affect the exocytosis of immediately available synaptic vesicles at the active zone.
Collapse
Affiliation(s)
- X H Wang
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | | | | |
Collapse
|
12
|
Miyamoto S. Changes in mobility of synaptic vesicles with assembly and disassembly of actin network. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1244:85-91. [PMID: 7766673 DOI: 10.1016/0304-4165(94)00199-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In a presynaptic terminal, neurotransmitters are stored in synaptic vesicles and secreted into the synaptic cleft as a final step of cell signal transduction. At a static state, the vesicles are retained in the highly dense actin network. Prior to exocytosis, the dense actin network must disassemble or largely be organized. Actin networks are formed in vitro which retain synaptic vesicles prepared from rat cerebral cortex. Dynamic behaviors of synaptic vesicles are measured by the dynamic light scattering method. The D(app) values of synaptic vesicles confined in actin network became less than 1/4 those of free vesicles. The motions of synaptic vesicles are substantially restricted. This means that synaptic vesicles which are liberated from the actin network by detachment of synapsin 1 molecules are still trapped in the cage-like space of actin filaments. The actin network is disassembled by the actin severing protein, gelsolin, which is activated in the presence of microM level free Ca2+ ions. The D(app)(v) values of synaptic vesicles after severing the actin network return to those of free vesicles in the presence of short actin fragments. A molecular model for exocytosis in the synaptic terminal is constructed on the basis of these results.
Collapse
Affiliation(s)
- S Miyamoto
- Department of Biochemical Engineering, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka, Japan
| |
Collapse
|
13
|
Abstract
Small actin monomer binding proteins are essential components of the actin polymerization machinery. Originally thought of as passive buffers that prevent polymerization of actin monomers, recent discoveries elucidate how some actin monomer binding proteins can promote as well as inhibit polymerization, and how they cooperate to regulate actin assembly.
Collapse
Affiliation(s)
- H Q Sun
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas 75235-9040, USA
| | | | | |
Collapse
|
14
|
Sussman MA, Sakhi S, Tocco G, Najm I, Baudry M, Kedes L, Schreiber SS. Neural tropomodulin: developmental expression and effect of seizure activity. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1994; 80:45-53. [PMID: 7955359 DOI: 10.1016/0165-3806(94)90088-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Tropomodulin is a 40.6 kDa tropomyosin-binding protein associated with actin filaments in muscle and the membrane cytoskeleton in erythrocytes. We have detected tropomodulin mRNA and protein in brains of rats by northern and western blot analyses. In situ hybridization of rat brain and spinal cord sections shows tropomodulin expression in the cerebellum, neocortex, hippocampus, and anterior horn of the spinal cord. Tropomodulin expression is first observed around day 15 after birth and increases through day 24. The temporal and spatial changes in tropomodulin expression during cerebellar development parallel those for brain tropomyosin. Tropomodulin mRNA increases in the dentate gyrus of the hippocampus following prolonged seizure activity induced by kainic acid administration; the increase is clearly evident 8 h after initiation of seizures and is still present 1 week later. However, Western blot analysis of tropomodulin protein level in the dentate gyrus before and after seizure induction show only slight increases in tropomodulin protein concentration, suggesting tight regulation of tropomodulin expression at the translational level. The developmental expression of tropomodulin, together with the induction of tropomodulin mRNA production in the dentate gyrus after kainic acid treatment, suggests a role for tropomodulin in neuronal organization and plasticity.
Collapse
Affiliation(s)
- M A Sussman
- Institute for Genetic Medicine, University of Southern California, School of Medicine, Los Angeles 90033
| | | | | | | | | | | | | |
Collapse
|
15
|
Membrane and Cytoskeleton Flow in Motile Cells with Emphasis on the Contribution of Free-Living Amoebae. INTERNATIONAL REVIEW OF CYTOLOGY 1994. [DOI: 10.1016/s0074-7696(08)62405-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
16
|
Faivre-Sarrailh C, Lena JY, Had L, Vignes M, Lindberg U. Location of profilin at presynaptic sites in the cerebellar cortex; implication for the regulation of the actin-polymerization state during axonal elongation and synaptogenesis. JOURNAL OF NEUROCYTOLOGY 1993; 22:1060-72. [PMID: 8106880 DOI: 10.1007/bf01235749] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Profilin is a 15 kDa protein that binds actin monomers and inhibits their polymerization in vitro. The actin-profilin complex can be rapidly dissociated in vitro by phosphatidylinositol-4,5-bis-phosphate, providing a mechanism for regulating actin assembly-disassembly cycles during cell motile events. We have used a polyclonal antibody to calf spleen profilin to analyse the developmental expression and cellular distribution of profilin in the rat cerebellum and cultured cortical neurons. Immature neurons contain large amount of profilin both in vivo and in vitro. Immunofluorescence showed it to be present in developing neurites and growth cones but not in the filopodia of cortical neurons in culture. Profilin immunoreactivity was intense in the parallel fibres, the granule cell axons of the cerebellar cortex, at the time when they are elongating. Purkinje cell dendrites were not labelled. Profilin immunostaining was present in presynaptic varicosities, but not in dendritic spines within the molecular layer of juvenile and adult rats. The profilin concentration was higher in synaptosomes than in the total cerebellum during the second and third postnatal weeks, a period of intense synaptogenesis. Thus, profilin may help regulate actin polymerization and depolymerization during axonal elongation and synaptogenesis. Its restriction to the presynaptic site in the adult suggests that it may also be involved in the regulation of the release of synaptic vesicles.
Collapse
Affiliation(s)
- C Faivre-Sarrailh
- Laboratoire de Neurobiologie Endocrinologique, URA 1197 CNRS, Université Montpellier II, France
| | | | | | | | | |
Collapse
|
17
|
Affiliation(s)
- T Obinata
- Department of Biology, Faculty of Science, Chiba University, Japan
| |
Collapse
|
18
|
Bray JJ, Fernyhough P, Bamburg JR, Bray D. Actin depolymerizing factor is a component of slow axonal transport. J Neurochem 1992; 58:2081-7. [PMID: 1374117 DOI: 10.1111/j.1471-4159.1992.tb10949.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We examined the low molecular weight proteins transported with actin in the chicken sciatic nerve after injection of [35S]methionine into the lumbar spinal cord. A prominent component of slow axonal transport with apparent molecular mass 19 kDa comigrated on two-dimensional gels with chicken actin depolymerizing factor (ADF), previously shown to be a major actin-binding protein in brain. There was comparatively little radioactivity associated with the actin monomer sequestering proteins, profilin or cofilin, and examination of the rapid component of axonal transport failed to reveal appreciable quantities of actin, ADF, profilin, or cofilin. These results show that both actin and ADF are carried by slow axonal transport and raise the possibility that actin travels within the axon in an unpolymerized form in a complex with ADF.
Collapse
Affiliation(s)
- J J Bray
- MRC Cell Biophysics Unit, London, England
| | | | | | | |
Collapse
|
19
|
Fifková E, Morales M. Actin matrix of dendritic spines, synaptic plasticity, and long-term potentiation. INTERNATIONAL REVIEW OF CYTOLOGY 1992; 139:267-307. [PMID: 1428678 DOI: 10.1016/s0074-7696(08)61414-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- E Fifková
- Department of Psychology, University of Colorado, Boulder 80309
| | | |
Collapse
|
20
|
Léna JY, Bamburg JR, Rabié A, Faivre-Sarrailh C. Actin-depolymerizing factor (ADF) in the cerebellum of the developing rat: a quantitative and immunocytochemical study. J Neurosci Res 1991; 30:18-27. [PMID: 1795402 DOI: 10.1002/jnr.490300104] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A specific antiserum against actin-depolymerizing factor (ADF) was used in a quantitative and immunocytochemical study of ADF in the cerebellum of developing rats. The Triton-soluble ADF concentration remained stable throughout development. Light and electron microscopic immunocytochemistry showed that ADF was not detected in all cerebellar cells. ADF immunoreactivity was found in Purkinje cells, but not in granule cells. It was found in the Bergmann astrocytes and the astrocytes of the white matter, but not in the oligodendrocytes. The cell bodies and dendrites of Purkinje cells were immunoreactive for ADF but the axons were not. In contrast, the other axons of the white matter (mossy and climbing fibres) were labeled. Thus, ADF was not restricted to either the dendritic or axonal compartments. However, dendritic spines and postsynaptic densities were immunoreactive, whereas presynaptic varicosities were unlabeled. The immunoreactivities for ADF and actin were compared. ADF staining was uniformly distributed throughout the entire dendritic arborization of the Purkinje cell, while filamentous actin is highly concentrated in the dendritic spines, indicating that ADF activity might vary according to its cellular localization.
Collapse
Affiliation(s)
- J Y Léna
- Laboratoire de Neurobiologie Endocrinologique, URA 1197 CNRS, Université Montpellier II, Sciences et Techniques du Languedoc, France
| | | | | | | |
Collapse
|
21
|
Abstract
Cytoskeletal proteins--neurofilament polypeptides, tubulin and actin--are transported along axons by slow transport. How or in what form they are transported is not known. One hypothesis is that they are assembled into the cytoskeleton at the cell body and transported as intact polymers down the axon. However, recent radiolabeling and photobleaching studies have shown that tubulin and actin exist in both a mobile phase and a stationary phase in the axon. Consequently, it is more likely that cytoskeletal proteins move along the axon in some form of transport complex and are assembled into a cytoskeleton which is stationary. In this overview we discuss these topics and consider the evidence for the existence of transport complexes associated with slow axonal flow. Such evidence includes the slow transport of particulate complexes containing tubulin and neurofilament polypeptides along reconstituted microtubules in vitro, and the coordinate slow transport of actin with actin-binding proteins in vivo.
Collapse
Affiliation(s)
- J J Bray
- Neuroscience Centre, University of Otago Medical School, Dunedin, New Zealand
| | | |
Collapse
|
22
|
Faivre-Sarrailh C, Had L, Ferraz C, Sri Widada JS, Liautard JP, Rabié A. Expression of tropomyosin genes during the development of the rat cerebellum. J Neurochem 1990; 55:899-906. [PMID: 2384759 DOI: 10.1111/j.1471-4159.1990.tb04576.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The expression of the tropomyosin genes in the rat nervous system was examined during the postnatal development of the cerebellum, using human-specific alpha-, beta-, gamma-, and delta-tropomyosin cDNA probes and rat-specific alpha-, beta-, and delta-tropomyosin oligonucleotide probes. The beta- and gamma-genes do not seem to be expressed in the rat brain. The delta-tropomyosin gene produces two mRNAs: a major one of 2.4 kb, which is highly concentrated during the first postnatal week and then decreases fourfold in level until the age of 35 days, and a minor one of 2 kb, with the same developmental profile as the 2.4-kb mRNA. A 3-kb mRNA is expressed by the alpha-tropomyosin gene and is characteristic of the mature rat. The expression of the tropomyosin genes during the development of the rat cerebellum does not seem to be regulated through alternative splicing but rather implies the differential expression of two different isogenes. The multiple isoforms of tropomyosin produced during neuronal differentiation may be intimately involved in the regulation of the organization and function of actin microfilaments.
Collapse
Affiliation(s)
- C Faivre-Sarrailh
- Laboratoire de Neurobiologie Endocrinologique, URA 1197 CNRS, Université de Montpellier II, France
| | | | | | | | | | | |
Collapse
|
23
|
Abstract
Expression of profilin and profilin:actin ratios in vertebrates were determined with polyclonal antibodies against profilin and actin. Profilin was detected in a wide variety of bovine tissues and was enriched in smooth muscle of bovine, porcine and avian origin. The protein was purified from pig stomach muscle tissue. Smooth muscle profilin was found to be more effective in inhibiting the polymerization of skeletal muscle actin than thymus profilin purified by the same method.
Collapse
Affiliation(s)
- F Buss
- Developmental Biology Unit, University of Bielefeld, FRG
| | | |
Collapse
|
24
|
Larsson H, Lindberg U. The effect of divalent cations on the interaction between calf spleen profilin and different actins. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 953:95-105. [PMID: 3342244 DOI: 10.1016/0167-4838(88)90013-1] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The interaction between calf spleen profilin and actin depends critically on the status of the C-terminus of the actin, and in the case of profilin, the C-terminus is of great importance for the physiochemical behaviour of the protein. Both proteins easily lose their C-terminal amino acids during the preparation, and special care has to be taken to ensure the isolation of the proteins in the intact form. Another factor that may seriously influence the study of the interaction of profilin with actin is the presence of varying amounts of an activity that causes an apparent stabilization of the complex even at later stages of its purification. We have found conditions for the isolation of intact profilin and actin, and studied the interaction between the two proteins, including the determination of the Kdiss for the complex formed under various ionic conditions. The complex formed between profilin and actin from calf spleen was found to be significantly stronger (Kdiss less than or equal to 10(-8) M in 50 mM KCl, and Kdiss = 4.10(-7) M in 50 mM KCl, 1 mM MgCl2) than that formed between profilin and muscle alpha-actin (Kdiss = 10(-6) M in 50 mM KCl, +/- 1 mM MgCl2). The profilactin complex formed in the mammalian system was stronger than the complex formed between Acanthamoeba actin and the profilin-like protein isolated from this organism. Analysis of the formation of the calf spleen complex in the presence of varying concentrations of divalent cations gave evidence for the presence of a high-affinity divalent-cation-binding site on the spleen actin (beta, gamma) which appears to regulate the interaction with profilin.
Collapse
Affiliation(s)
- H Larsson
- Department of Zoological Cell Biology, Wenner-Gren Institute, University of Stockholm, Sweden
| | | |
Collapse
|
25
|
Ampe C, Markey F, Lindberg U, Vandekerckhove J. The primary structure of human platelet profilin: reinvestigation of the calf spleen profilin sequence. FEBS Lett 1988; 228:17-21. [PMID: 3342873 DOI: 10.1016/0014-5793(88)80575-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The primary structure of human platelet profilin was determined by aligning the sequences of its tryptic peptides to the previously determined calf spleen profilin sequence [(1979) FEBS Lett. 101, 161-165]. Comparison of the peptide fingerprints of the two proteins suggested a higher homology than that found by direct sequence comparison. We therefore reinvestigated the sequences of the peptides from calf spleen profilin. We identified four incorrect charge assignments and a deletion of three residues. The similarity between the two vertebrate profilins amounts to 95%.
Collapse
Affiliation(s)
- C Ampe
- Laboratorium voor Genetica, Rijksuniversiteit Gent, Belgium
| | | | | | | |
Collapse
|
26
|
Ampe C, Sato M, Pollard TD, Vandekerckhove J. The primary structure of the basic isoform of Acanthamoeba profilin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 170:597-601. [PMID: 3338456 DOI: 10.1111/j.1432-1033.1988.tb13739.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Acanthamoeba profilin-II [Kaiser, D.A., Sato, M., Ebert, R. F. and Pollard, T.D. (1986) J. Cell. Biol. 102, 221-226] was digested with trypsin or cleaved by 2-(2-nitrophenylsulphenyl)-3-methyl-3-bromoindolenine. The tryptic peptides were purified by reversed-phase-high-performance liquid chromatography and completely sequenced using automated gas-phase sequence analysis. The complete profilin-II sequence was deduced by ordering the tryptic peptides using the sequence information of the tryptophan-cleavage products. Acanthamoeba profilin-II was found to be homologous to the previously determined profilin-I sequence [Ampe, C., Vandekerckhove, J., Brenner, L., Tobacman, L. and Korn, E.D. (1985) J. Biol. Chem. 260, 834-840]. Like profilin-I, profilin-II consists of 125 amino acids, has a blocked NH2 terminus and a trimethyllysine residue at position 103. Profilin-II differs in at least 21 positions from one of the profilin-I isoforms. The amino acid exchanges are mainly concentrated in the middle part of the sequence. Profilin-II contains two more basic residues than profilin-I, which explains its higher isoelectric point.
Collapse
Affiliation(s)
- C Ampe
- Laboratory of Genetics, State University Ghent, Belgium
| | | | | | | |
Collapse
|
27
|
Abstract
Actin depolymerizing factor (ADF) is a low molecular mass (19 kD) protein that forms a tightly bound dimeric complex with actin. We have raised a rabbit antiserum to chick brain ADF and used it to analyze the distribution and cellular localization of ADF. We find that ADF is a major constituent of all chick embryonic and most adult tissues examined, accounting for 0.1-0.4% of the total protein. Some tissues have as much as 0.6 mol ADF per mole actin. Adult heart and skeletal muscle are unusual in having very low levels of ADF: less than 0.02% of the soluble protein. During the development of skeletal muscle, ADF levels are maximal up to approximately 11 d in ovo and then decline to reach their adult levels by 14 d posthatching. Brain tissue and cultured cell lines from several other vertebrates, including mammals, all possess proteins of identical size to ADF that are recognized by the ADF antiserum. No proteins are specifically recognized by the ADF antiserum in extracts from Acanthamoeba castellanii or from nerve tissue of several invertebrates. Indirect immunofluorescence shows that ADF is present throughout the cytosol of most cells and at the leading edge of ruffled membranes and in the neuronal growth cone. Its abundance and widespread distribution together with its ability to sequester actin molecules, even those in an already polymerized state, suggest that ADF is a major factor in the regulation of actin filaments in many vertebrate cells.
Collapse
Affiliation(s)
- J R Bamburg
- Medical Research Council Cell Biophysics Unit, Kings College, London, England
| | | |
Collapse
|
28
|
|
29
|
Kaiser DA, Sato M, Ebert RF, Pollard TD. Purification and characterization of two isoforms of Acanthamoeba profilin. J Biophys Biochem Cytol 1986; 102:221-6. [PMID: 3941153 PMCID: PMC2114039 DOI: 10.1083/jcb.102.1.221] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Acanthamoeba profilin purified according to E. Reichstein and E.D. Korn (1979, J. Biol. Chem. 254:6174-6179) consists of two isoforms (profilin-I and-II) with approximately the same molecular weight and reactivity to a monoclonal antibody but different isoelectric points and different mobilities on carboxymethyl-agarose chromatography and reversed-phase high-performance liquid chromatography. The isoelectric points of profilin-I is approximately 5.5 and that of profilin-II is greater than or equal to 9.0. Tryptic peptides from the two proteins are substantially different, which suggests that there are major differences in their sequences. At similar concentrations, both profilins prolong the lag phase at the outset of spontaneous polymerization and inhibit the extent of polymerization. Both forms also inhibit elongation weakly at the barbed end and strongly at the pointed end of actin filaments.
Collapse
|