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The Journal of Bone & Joint Surgery, Volume 83, Issue 1 suppl 1

Scientific Article | March 01, 2001

The Effect of BMP on the Expression of Cytoskeletal Proteins and Its Potential Relevance

Ruth L. Vinall, PhD; A. Hari Reddi, PhD

From Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, School of Medicine, University of California Davis, Sacramento, California
Ruth L. Vinall, PhD A. Hari Reddi, PhD Center for Tissue Regeneration and Repair, Research Building I, Room 2000, 4635 Second Avenue, School of Medicine, University of California Davis, Sacramento, CA 95817. E-mail address for R.L. Vinall: ruth.vinall@ucdmc.ucdavis.edu
In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the Lawrence J. Ellison Chair. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

The Journal of Bone & Joint Surgery. 2001; 83:S63-S69

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Introduction

Bone morphogenetic proteins (BMPs) govern the development of the basic form and pattern of the skeleton by way of specific modulation of cells within defined regions of the embryo ^1,2 . BMPs may affect skeletal development by influencing cell shape or cytoskeletal organization, or both. It is well known that profound changes in cell shape are associated with development of the skeleton. The cartilage consists of extracellular matrix and component chondrocytes. The chondrocytes interact with the extracellular matrix. The extracellular signals, including growth factors, morphogens, and mechanical signals, influence chondrocyte shape and function. Chondrocyte shape is determined by the cytoskeleton. The cytoskeleton is the endoskeleton of the chondrocyte and other cells.

In chondrocytes, there is a strong relationship between cell shape, cytoskeletal organization, and cell phenotype ³ . Like most vertebrate cells, chondrocytes express three main types of cytoskeletal protein filaments: actin microfilaments, intermediate filaments, and microtubules. These filaments form interacting networks within cells. Actin microfilaments are essential for cell movement and are key players in cell-cell and cell-matrix adhesion junctions. Intermediate filaments provide cells with mechanical strength. Microtubules are structures that are essential for cell division and for intracellular transport. The functionality of the complex networks formed by these three types of filaments is dependent on a vast number of accessory proteins. These cytoskeletal proteins play diverse roles within the cell. For example, some cytoskeletal proteins allow interaction between the three protein filament networks and some allow for attachment to the cell membrane, whereas others function as motors that move organelles along the protein filaments or move the filaments themselves. The function of the cytoskeleton is not purely structural. It has been demonstrated in a number of cell types that organization of the cytoskeleton can be influenced by external factors and that changes in organization of the cytoskeleton are able to influence gene expression. The ability of the cytoskeleton to influence gene expression has been studied extensively in chondrocytes.

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Fig. 1:: Chondrocytes are exposed to a number of physical and biochemical external stimuli that can affect their phenotype, such as matrix components, mechanical forces, and growth factors and cytokines. These external stimuli may, in part, affect chondrocyte phenotype by altering the organization of the chondrocyte cytoskeleton. Previous studies have demonstrated that alterations in organization of the chondrocyte cytoskeleton affect chondrocyte phenotype ^7,8 . Our data suggest that the expression and distribution of focal adhesion junctions also affect chondrocyte phenotype. Focal adhesion junctions facilitate connection of the actin cytoskeleton to the surrounding matrix (review; Burridge and Chrzanowska-Wodnicka ³⁸ ). They comprise an intracellular domain that links to the actin cytoskeleton and a transmembrane domain that links to the extracellular matrix. Many proteins participate in forming the cytoplasmic adhesion plaque ¹⁸ . Some of these proteins have predominantly structural roles, whereas others are involved in signal transduction. Some do both. Members of the integrin family make up the transmembrane domain. Integrins are heterodimers that consist of a and ß subunits ³⁹ .

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Fig. 2:: Chondrocytes grown in monolayer culture (left vertical panel) and suspension culture (right vertical panel) displayed different patterns of labeling for tensin, talin, paxillin, and focal adhesion kinase (FAK). In monolayer culture, large areas of punctate membrane-associated labeling were observed. Labeling appeared to be polarized, and "streaks" of punctate labeling for tensin, talin, paxillin, and FAK appeared to align to the extended edges of the cells. In suspension culture, punctate labeling for tensin, talin, paxillin, and FAK was also observed; however, the areas of punctate labeling were much smaller than those observed in monolayer culture and the number of labeled areas was much greater.

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Fig. 3:: Chondrocytes grown in suspension culture (confocal section series from the upper (A) to the lower (I) surface of the chondrocytes, scale µ5 m). The actin microfilaments form a complex mesh of relatively thin actin microfilaments that completely surround the chondrocyte nucleus.

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Fig. 4:: Chondrocytes grown in monolayer culture (confocal section series from the upper (A) to the lower (D) surface of the chondrocyte, scale bar = 5 µm). The actin microfilaments form thick struts that extend from the edges of the flattened chondrocytes. The majority of the actin microfilaments are located at the lower surface of the chondrocyte, i.e., the surface adjacent to the culture dish.

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TABLE I: Components of Cytoskeleton in Chondrocytes

Cytoskeletal protein	Molecular weight	Interactions	Reference
Tensin	2100 kD	Actin, SH2-binding proteins, vinculin	Van de Werken et al. ⁴⁰
Talin	235 kD	Actin, ß1 integrin, vinculin	Luo et al. ²⁹
Paxillin	68 kD	Vinculin, FAK, SH2-binding proteins	Shakibaei et al. ³⁰
Focal adhesion kinase (FAK)	125 kD	Integrins, paxillin	Clancy et al. ³¹ , Shakibaei et al. ³⁰
Vinculin	117 kD	Actin, alpha-actinin, talin, paxillin	Luo et al. ²⁹ , Shakibaei et al. ³⁰
Alpha-actinin	100 kD	Actin, ß1 integrin	Shakibaei et al. ³⁰
Integrins (a5ß1, a1ß1, a2ß1, a10ß1, a6ß1, aVß3)	Each subunit between 110 and 180 kD	Talin, FAK, alpha-activin	Loeser ⁴¹

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TABLE I: Components of Cytoskeleton in Chondrocytes

Cytoskeletal protein	Molecular weight	Interactions	Reference
Tensin	2100 kD	Actin, SH2-binding proteins, vinculin	Van de Werken et al. ⁴⁰
Talin	235 kD	Actin, ß1 integrin, vinculin	Luo et al. ²⁹
Paxillin	68 kD	Vinculin, FAK, SH2-binding proteins	Shakibaei et al. ³⁰
Focal adhesion kinase (FAK)	125 kD	Integrins, paxillin	Clancy et al. ³¹ , Shakibaei et al. ³⁰
Vinculin	117 kD	Actin, alpha-actinin, talin, paxillin	Luo et al. ²⁹ , Shakibaei et al. ³⁰
Alpha-actinin	100 kD	Actin, ß1 integrin	Shakibaei et al. ³⁰
Integrins (a5ß1, a1ß1, a2ß1, a10ß1, a6ß1, aVß3)	Each subunit between 110 and 180 kD	Talin, FAK, alpha-activin	Loeser ⁴¹

Cell Shape and Organization of the Cytoskeleton Influence Chondrocyte Phenotype

In 1969, Chacko et al. ⁴ reported that repeated passaging of freshly isolated chick chondrocytes resulted in loss of the polygonal morphology characteristic of cultured chondrocytes and promotion of a flattened, spindle-shaped morphology. The loss of chondrocyte morphology was accompanied by the loss of type II collagen expression, a marker of chondrocyte phenotype, and promotion of type I collagen expression, a marker of chondrocyte de-differentiation ^5,6 . The actin cytoskeleton is in fact responsible for changes in chondrocyte phenotype. Elegant studies by Horton and Hassell ⁷ and Brown and Benya ⁸ demonstrated that manipulation of the actin cytoskeleton could influence chondrocyte phenotype in the absence of change in cell shape. These data indicated that changes in the organization of the actin cytoskeleton were independent of secondary cell shape changes. Horton and Hassell ⁷ induced de-differentiation of rounded chondrocytes by the addition of retinoic acid. Brown and Benya ⁸ demonstrated that the addition of dihydrocytochalasin B, a drug known to alter the actin microfilament architecture, to flattened, dedifferentiated chondrocytes, at a concentration that caused alteration in organization of the actin cytoskeleton but did not alter chondrocyte shape, resulted in promotion of the chondrocyte phenotype. Interestingly, organization of microtubule and intermediate filament networks was not affected during modulation of chondrocyte phenotype by the addition of dihydrocytochalasin B, suggesting that under these conditions the actin cytoskeleton can act independently. Involvement of the actin cytoskeleton in modulation of chondrocyte phenotype has also been demonstrated in drug-free systems; Mallein-Gerin et al. demonstrated that monolayer-induced de-differentiation of chondrocytes resulted in a dramatic change in the organization of the actin cytoskeleton ⁹ .

The role that microtubules and intermediate filaments play in modulation of chondrocyte phenotype remains unclear, and considerably less research has focused on these components of the chondrocyte cytoskeleton compared with actin microfilaments. Immunolocalization studies have revealed that microtubules and intermediate filaments are most abundant in the rounded chondrocytes located in the transitional and deep zones of articular cartilage ^10-12 . Idowu et al. have shown by confocal analysis that there no significant difference in the organization of microtubules and intermediate filaments in monolayer (i.e., flattened) and suspension (i.e., rounded) cultured chondrocytes ¹³ . Brown and Benya also noted that the organization of microtubules appeared to remain unchanged during phenotypic modulation and that organization of intermediate filaments was not linked to phenotypic change ⁸ . These data suggest that changes in the organization of microtubule and intermediate filament networks are not involved in the modulation of chondrocyte phenotype; however, other studies have indicated that microtubule and intermediate filament networks can influence chondrocyte phenotype. For example, Farquharson et al. demonstrated a dramatic increase in the expression of microtubules in hypertrophic chondrocytes ¹⁴ . This suggests that microtubules may be involved in hypertrophy of chondrocytes. When microtubule and actin networks are disrupted, transmission of load to the nucleus is maintained, indicating that the intermediate filament network may also be able to influence chondrocyte phenotype ^15,16 .

Chondrocyte Cytoskeleton and Integrins

Chondrocytes are exposed to a number of physical and biochemical external stimuli that can affect their phenotype. The organization of the actin cytoskeleton is responsive to many of these stimuli because the cytoskeleton is "hard-wired" to the surrounding extracellular matrix by cell-matrix junctions. The most common type of cell-matrix junction is a focal adhesion junction ( Fig. 1 ) ^17,18 . Focal adhesions comprise an intracellular domain that allows for linkage of the junction to the actin cytoskeleton, a transmembrane domain (integrin) that confers specificity to the junction, and an extracellular domain that is an extracellular matrix component. The intracellular domain consists of a complex of proteins, some purely structural in nature and others involved in signal transduction pathways. Some proteins perform both functions.

Due to "hard-wiring" of the chondrocyte cytoskeleton to its surrounding matrix, environmental factors, such as compression-induced movement of the extracellular matrix and factors that affect binding of chondrocytes to the extracellular matrix by cell-matrix junctions, affect organization of the cytoskeleton and therefore chondrocyte phenotype. Enomoto et al. ¹⁹ demonstrated that ß1 integrin mediates chondrocyte interaction with type I collagen, type II collagen, and fibronectin. They noted that chondrocyte adhesiveness and chondrocyte morphology differed when chondrocytes were cultured on different types of extracellular matrix. This result implies that changes in matrix composition may influence expression of cell-matrix junction components and cell shape and therefore organization of the actin cytoskeleton.

A number of growth factors and cytokines that are known to influence chondrocyte phenotype have also been shown to influence chondrocyte adhesion and the expression levels of chondrocyte-associated integrins. Loeser ²⁰ demonstrated that retinoic acid decreases the attachment of chondrocytes to matrix proteins and that transforming growth factor beta (a6-b) increases the attachment of chondrocytes to matrix proteins. Further studies demonstrated that the alteration in attachment was due to TGF-ß and retinoic acid-induced changes in integrin expression ²¹ . Although the effect of TGF-ß and retinoic acid on organization of the actin cytoskeleton was not assessed during these studies, the observed changes in adhesiveness of the chondrocytes and changes in integrin expression imply that the actin cytoskeleton was affected.

It has been demonstrated in a number of cell types that mechanical stimulation of cells results in changes in the organization of the cytoskeleton ²² . In vivo , chondrocytes are exposed to both cyclical and continuous compressive forces that are able to affect their phenotype. It has been demonstrated that mechanical forces are able to alter the shape and influence the cytoskeletal organization of chondrocytes. Guilak et al. ²³ demonstrated by microscopic imaging studies that chondrocytes and their nuclei undergo shape and volume changes in a coordinated manner with deformation of the tissue matrix. Wright et al. ²⁴ demonstrated that a5ß1 integrin expression is affected by mechanical stimulation. At the cellular level, Maniotis et al. ¹⁵ demonstrated that when integrins are pulled with micromanipulating beads, cytoskeletal filaments reorientate, nuclei distort, and nucleoli redistribute along the axis of applied tension.

BMPs Stimulate Expression of Cytoskeletal Proteins

As part of our study of chondrocyte cytoskeleton, we have examined the relationship between the expression of cytoskeletal proteins involved in the intracellular linkage of focal adhesions to the actin cytoskeleton and the chondrocyte phenotype ( Fig. 1 and Table I ). In our recent studies, we determined that suspension culture of chondrocytes and treatment of chondrocytes with BMP7-i.e., conditions that promote chondrocyte phenotype-resulted in increased expression of the cytoskeletal components tensin, talin, paxillin, and focal adhesion kinase (FAK) and of type II collagen, a marker of chondrocyte phenotype . We also demonstrated that disruption of the chondrocyte actin cytoskeleton with cytochalasin D led to BMP7-mediated increase in expression of tensin, talin, paxillin, and FAK and type II collagen. Interestingly, our immunohistochemical data revealed that the distribution of tensin, talin, paxillin, and FAK differed considerably between monolayer and suspension-cultured chondrocytes, i.e., conditions that have opposite effects on chondrocyte phenotype ( Fig. 2 ). In monolayer culture, large areas of punctate membrane-associated labeling were observed. Labeling appeared to be polarized, and "streaks" of punctate labeling for tensin, talin, paxillin, and FAK appeared to align to the extended edges of the cells. In suspension culture, punctate labeling for tensin, talin, paxillin, and FAK was also observed; however, the areas of punctate labeling were much smaller than those observed in monolayer culture and the number of labeled areas was much greater. Organization of the actin cytoskeleton also differed in suspension and monolayer-cultured chondrocytes. In suspension culture, actin microfilaments formed a complex mesh of multiple thin filaments around the chondrocyte nucleus ( Fig. 3 ). In contrast, in monolayer culture actin microfilaments appeared much thicker but less abundant ( Fig. 4 ). From these data, we conclude that expression levels of cytoskeletal proteins involved in focal adhesions influence chondrocyte phenotype and that expression levels of cytoskeletal proteins may be altered by factors known to affect chondrocyte phenotype. We think it likely that alterations in cytoskeletal proteins associated with focal adhesions influence organization of the actin cytoskeleton, a factor known to affect chondrocyte phenotype. Inhibition of BMP7-induced promotion of chondrocyte phenotype by disruption of the actin cytoskeleton supports our hypothesis. Our hypothesis is also supported by data from studies on other cell types demonstrating that expression of focal adhesion proteins and organization of the actin cytoskeleton are tightly linked ^15,25-27 . The ability of BMP7 to modulate chondrocyte phenotype by altering the expression of cytoskeletal proteins is somewhat surprising. Interestingly, it has been demonstrated in other cell types that growth factors and cytokines, e.g., insulin-like growth factor-1 (IGF-1) and interleukin-1 (IL-1), interact with cytoskeletal proteins ^28-30 .

Conclusions

Cytoskeletal proteins clearly are important determinants of chondrocyte phenotype. Further understanding of the relationship between components of the cytoskeleton and growth factors/cytokines and other external factors that affect chondrocyte phenotype may aid in the development of new strategies to deal with diseases such as arthritis.

The involvement of cytoskeletal proteins in signal transduction pathways that are able to influence gene expression has not been discussed. We take this opportunity to emphasize the importance of signal transduction pathways in the control of chondrocyte phenotype. Signal transduction pathways and changes in organization of the actin cytoskeleton are both stimulated by binding of focal adhesions to matrix components. It is extremely likely that alterations in chondrocyte phenotype are a result of the combined influence of these two events ^29,31-34 .

Finally, it is appropriate to comment on some data that were presented at the BMP conference. Francis-West et al. ³⁵ reported that GDF-5 promotes initiation of chondrogenesis by increasing cell adhesion in a subpopulation of cells. Takahashi et al. ³⁶ reported that calponin, an actin-binding protein, may be involved in negative regulation of BMP signaling pathway. The actin-binding domain was essential for negative regulation. Liu et al. ³⁷ reported that Smad3 can interact with HEF1, an adapter protein that is implicated in multiple signaling pathways such as those mediated by integrin receptors. Taken together, these data support our hypothesis that components of the chondrocyte cytoskeleton are critical in BMP signaling during development and maintenance of articular cartilage.

References

ReddiAH. Cartilage morphogenesis: role of bone and cartilage morphogenetic proteins, homeobox genes and extracellular matrix. Matrix Biol,1995;14: 599-S606. 14599 1995 [PubMed]

Francis-West PH, Parish J, Lee K,Archer CW. BMP/GDF-signalling interactions during synovial joint development. Cell Tissue Res,1999;296: 111-S9. 296111 1999 [PubMed]

Ben-Ze'ev A. Animal cell shape changes and gene expression. Bioessays,1991;13: 207-S12. 13207 1991 [PubMed]

ChackoS, Abbott J, Holtzer S,Holtzer H. The loss of phenotypic traits by differentiated cells. VI. Behavior of the progeny of a single chondrocyte. J Exp Med,1969;130: 417-S42. 130417 1969 [PubMed]

MayneR, Vail MS, Mayne PM,Miller EJ. Changes in type of collagen synthesized as clones of chick chondrocytes grow and eventually lose division capacity. Proc Natl Acad Sci U S A,1976;73: 1674-S8. 731674 1976 [PubMed]

von der MarkK, Gauss V, von der Mark H,Muller P. Relationship between cell shape and type of collagen synthesised as chondrocytes lose their cartilage phenotype in culture. Nature,1977;267: 531-S2. 267531 1977 [PubMed]

HortonW,Hassell JR. Independence of cell shape and loss of cartilage matrix production during retinoic acid treatment of cultured chondrocytes. Dev Biol,1986;115: 392-S7. 115392 1986 [PubMed]

BrownPD,Benya PD. Alterations in chondrocyte cytoskeletal architecture during phenotypic modulation by retinoic acid and dihydrocytochalasin B-induced reexpression. J Cell Biol,1988;106: 171-S9. 106171 1988 [PubMed]

Mallein-Gerin F, Garrone R,van der Rest M. Proteoglycan and collagen synthesis are correlated with actin organization in dedifferentiating chondrocytes. Eur J Cell Biol,1991;56: 364-S73. 56364 1991 [PubMed]

PalfreyAJ,Davies DV. The fine structure of chondrocytes. J Anat,1966;100: 213-S26. 100213 1966 [PubMed]

BenjaminM, Archer CW,Ralphs JR. Cytoskeleton of cartilage cells. Microsc Res Tech,1994;28: 372-S7. 28372 1994 [PubMed]

DurrantLA, Archer CW, Benjamin M,Ralphs JR. Organisation of the chondrocyte cytoskeleton and its response to changing mechanical conditions in organ culture. J Anat,1999;94: 343-S53. 94343 1999

IdowuBD, Knight MM, Bader DL,Lee DA. Confocal analysis of cytoskeletal organisation within isolated chondrocyte sub-populations cultured in agarose. Histochem J,2000;32: 165-S74. 32165 2000 [PubMed]

FarquharsonC, Lester D, Seawright E, Jefferies D,Houston B. Microtubules are potential regulators of growth-plate chondrocyte differentiation and hypertrophy. Bone,1999;25: 405-S12. 25405 1999 [PubMed]

ManiotisAJ, Chen CS,Ingber DE. Demonstration of mechanical connections between integrins, cytoskeletal filaments, and nucleoplasm that stabilize nuclear structure. Proc Natl Acad Sci U S A,1997;94: 849-S54. 94849 1997 [PubMed]

JanmeyPA. The cytoskeleton and cell signalling: component localization and mechanical coupling. Physiol Rev,1998;78: 763-S81. 78763 1998 [PubMed]

BurridgeK, Fath K, Kelly T, Nuckolls G,Turner C. Focal adhesions: transmembrane junctions between the extracellular matrix and the cytoskeleton. Annu Rev Cell Biol,1988;4: 487-S525. 4487 1988 [PubMed]

JockuschBM, Bubeck P, Giehl K, Kroemker M, Moschner J, Rothkegel M, Rudiger M, Schluter K, Stanke G,Winkler J. The molecular architecture of focal adhesions. Annu Rev Cell Dev Biol,1995;11: 379-S416. 11379 1995 [PubMed]

EnomotoM, Leboy PS, Menko AS,Boettiger D. Beta 1 integrins mediate chondrocyte interaction with type I collagen, type II collagen, and fibronectin. Exp Cell Res,1993;205: 276-S85. 205276 1993 [PubMed]

LoeserRF. Modulation of integrin-mediated attachment of chondrocytes to extracellular matrix proteins by cations, retinoic acid, and transforming growth factor beta. Exp Cell Res,1994;211: 17-S23. 21117 1994 [PubMed]

LoeserRF, Carlson CS,McGee MP. Expression of beta 1 integrins by articular cultured chondrocytes and in osteoarthritic cartilage. Exp Cell Res,1995;217: 248-S57. 217248 1995 [PubMed]

SchwartzMA,Ingber DE. Integrating with integrins. Mol Biol Cell,1994;5: 389-S93. 5389 1994 [PubMed]

GuilakF, Ratcliffe A,Mow VC. Chondrocyte deformation and local tissue strain in articular cartilage: a confocal microscope study. J Orthop Res,1995;13: 410-S21. 13410 1995 [PubMed]

WrightMO, Nishida K, Bavington C, Godolphin JL, Dunne E, Walmsley S, Jobanputra P, Nuki G,Salter DM. Hyperpolarisation of cultured human chondrocytes following cyclical pressure-induced strain: evidence of a role for a5ß1 integrin as a chondrocyte mechanoreceptor. J Orthop Res,1997;15: 742-S7. 15742 1997 [PubMed]

DashD, Aepfelbacher M,Siess W. Integrin alpha IIb beta 3-mediated translocation of CDC42Hs to the cytoskeleton in stimulated human platelets. J Biol Chem,1995;270(29): 17321-S6. 270(29)17321 1995

RoskelleyCD,Bissell MJ. Dynamic reciprocity revisited: a continuous, bidirectional flow of information between cells and the extracellular matrix regulates mammary epithelial cell function. Biochem Cell Biol,1995;73: 391-S7. 73391 1995 [PubMed]

TomasekJJ, Halliday NL, Updike DL, Ahern-Moore JS, Vu TK, Liu RW,Howard EW. Gelatinase A activation is regulated by the organization of the polymerized actin cytoskeleton. J Biol Chem,1997;272: 7482-S7. 2727482 1997 [PubMed]

LoeserRF. Growth factor regulation of chondrocyte integrins: differential effects of insulin-like growth factor 1 and transforming growth factor beta on alpha 1 beta 1 integrin expression and chondrocyte adhesions to type VI collagen. Arthritis Rheum,1997;40: 270-S6. 40270 1997 [PubMed]

LuoL, Cruz T,McCulloch C. Interleukin 1-induced calcium signalling in chondrocytes requires focal adhesions. Biochem J,1997;324 (Pt 2): 653-S8. 324 (Pt 2)653 1997 [PubMed]

ShakibaeiM, John T, De Souza P, Rahmanzadeh R,Merker HJ. Signal transduction by beta1 integrin receptors in human chondrocytes in vitro: collaboration with the insulin-like growth factor-I receptor. Biochem J,1999;342 Pt 3: 615-S23. 342 Pt 3615 1999 [PubMed]

ClancyRM, Rediske J, Tang X, Nijher N, Frenkel S, Philips M,Abramson SB. Outside-in signaling in the chondrocyte: nitric oxide disrupts fibronectin-induced assembly of a subplasmalemmal actin/rho A/focal adhesion kinase signaling complex. J Clin Invest,1997;100: 1789-S96. 1001789 1997 [PubMed]

JulianoRL,Haskill S. Signal transduction from the extracellular matrix. J Cell Biol,1993;120: 577-S85. 120577 1993 [PubMed]

RidleyAJ. Signal transduction through the GTP-binding proteins Rac and Rho. J Cell Sci Suppl,1994;18: 127-S31. 18127 1994 [PubMed]

CaryLA, Han DC,Guan J-L. Integrin-mediated signal transduction pathways. Histol Histopathol,1999;4: 1001-S9. 41001 1999

Francis-West PH, Abdelfattah A, Luyten FP, Archer CWThe role of GDF-5 during skeletal developmentBMP Conference 2000 , p 36.

Takahashi K, Yamamua H, Imamura T, Miyazono K, Yoshikawa HMice lacking smooth muscle calponin display increased bone formation that is associated with enhancement of BMP-responses: evidence for negative regulation of BMP-signalling by calponinBMP Conference 2000 , p 45.

Liu X, Elia AE, Golemis EA, Farley J, Wang TA novel cytoplasmic signaling mechanism of Smad3 to regulate proteasomal degradation of HEF1BMP Conference 2000 , p 76.

BurridgeK,Chrzanowska-Wodnicka M. 1996. Focal adhesions, contractility, and signaling. Annu Rev Cell Dev Biol,1996;12: 463-S518. 12463 1996 [PubMed]

HynesRO. Integrins: versatility, modulation, and signaling in cell adhesion. Cell,1992;69: 11-S25. 6911 1992 [PubMed]

van de WerkenR, Gennari M, Tavella S, Bet P, Molina F, Lin S, Cancedda R,Castagnola P. Modulation of tensin and vimentin expression in chick embryo developing cartilage and cultured differentiating chondrocytes. Eur J Biochem,1993;217: 781-S90. 217781 1993 [PubMed]

LoeserRF. Chondrocyte integrin expression and function. Biorheology,2000;37(1-2): 109-S16. 37(1-2)109 2000

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TABLE I: Components of Cytoskeleton in Chondrocytes

Cytoskeletal protein	Molecular weight	Interactions	Reference
Tensin	2100 kD	Actin, SH2-binding proteins, vinculin	Van de Werken et al. ⁴⁰
Talin	235 kD	Actin, ß1 integrin, vinculin	Luo et al. ²⁹
Paxillin	68 kD	Vinculin, FAK, SH2-binding proteins	Shakibaei et al. ³⁰
Focal adhesion kinase (FAK)	125 kD	Integrins, paxillin	Clancy et al. ³¹ , Shakibaei et al. ³⁰
Vinculin	117 kD	Actin, alpha-actinin, talin, paxillin	Luo et al. ²⁹ , Shakibaei et al. ³⁰
Alpha-actinin	100 kD	Actin, ß1 integrin	Shakibaei et al. ³⁰
Integrins (a5ß1, a1ß1, a2ß1, a10ß1, a6ß1, aVß3)	Each subunit between 110 and 180 kD	Talin, FAK, alpha-activin	Loeser ⁴¹

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TABLE I: Components of Cytoskeleton in Chondrocytes

Cytoskeletal protein	Molecular weight	Interactions	Reference
Tensin	2100 kD	Actin, SH2-binding proteins, vinculin	Van de Werken et al. ⁴⁰
Talin	235 kD	Actin, ß1 integrin, vinculin	Luo et al. ²⁹
Paxillin	68 kD	Vinculin, FAK, SH2-binding proteins	Shakibaei et al. ³⁰
Focal adhesion kinase (FAK)	125 kD	Integrins, paxillin	Clancy et al. ³¹ , Shakibaei et al. ³⁰
Vinculin	117 kD	Actin, alpha-actinin, talin, paxillin	Luo et al. ²⁹ , Shakibaei et al. ³⁰
Alpha-actinin	100 kD	Actin, ß1 integrin	Shakibaei et al. ³⁰
Integrins (a5ß1, a1ß1, a2ß1, a10ß1, a6ß1, aVß3)	Each subunit between 110 and 180 kD	Talin, FAK, alpha-activin	Loeser ⁴¹