Comparing the outcomes between Chopart, Lisfranc and multiple metatarsal shaft fractures.

OBJECTIVES: Complex midfoot injuries could lead to severe functional impairment of mobility and quality of daily living. Aim of this study was to compare the clinical and functional outcomes of Chopart, Lisfranc fractures and multiple metatarsal shaft fractures. DESIGN: Retrospective case series. SETTING: Level one trauma center. INTERVENTION: Open or closed reduction and internal fixation with screws, K-wires, plates, external fixation or combination of different technics. MAIN OUTCOME MEASUREMENTS: The American Orthopaedic Foot and Ankle Society (AOFAS) Midfoot Score and the Maryland Foot Score were used to assess pain and functional outcome. 3D gait analysis, pedobarographic analysis and radiologic examinations were performed. The activity level was measured by a step counting accelerometer. All results were compared to an age-matched healthy control group. RESULTS: 24 patients with a median age of 44 years (16-72) were included: 12 patients with multiple metatarsal shaft fractures, 6 patients with Chopart and 6 patients with Lisfranc fractures. The median follow-up was 2.6 years. The pedobarographic analysis reports reduced contact time of the total foot (p = 0.08), the forefoot (p = 0.008) and the hallux (p = 0.015) for the injured foot. A median score of 64 for the SF-36, 64 for the AOFAS Midfoot Score and 73 for the Maryland Foot Score indicated a poor restoration of foot function. Multiple metatarsal shaft fractures presented a significantly lower walking speed (p = 0.03) and cadence (p = 0.04). CONCLUSION: The worst results were reported for multiple metatarsal shaft fractures on outcome scores, pedobarography, gait analysis and activity. Metatarsal serial fractures should not be underestimated as well as Chopart and Lisfranc fractures. LEVEL OF EVIDENCE: Level IV.

Targeting of zyxin to sites of actin membrane interaction and to the nucleus.

The localization of proteins to particular intracellular compartments often regulates their functions. Zyxin is a LIM protein found prominently at sites of cell adhesion, faintly in leading lamellipodia, and transiently in cell nuclei. Here we have performed a domain analysis to identify regions in zyxin that are responsible for targeting it to different subcellular locations. The N-terminal proline-rich region of zyxin, which harbors binding sites for alpha-actinin and members of the Ena/VASP family, concentrates in lamellipodial extensions and weakly in focal adhesions. The LIM region of zyxin displays robust targeting to focal adhesions. When overexpressed in cells, the LIM region of zyxin causes displacement of endogenous zyxin from focal adhesions. Upon mislocalization of full-length zyxin, at least one member of the Ena/VASP family is also displaced, and the organization of the actin cytoskeleton is perturbed. Zyxin also has the capacity to shuttle between the nucleus and focal adhesion sites. When nuclear export is inhibited, zyxin accumulates in cell nuclei. The nuclear accumulation of zyxin occurs asynchronously with approximately half of the cells exhibiting nuclear localization of zyxin within 2.3 h of initiating leptomycin B treatment. Our results provide insight into the functions of different zyxin domains.

Molecular characterization of human zyxin.

Zyxin is a component of adhesion plaques that has been suggested to perform regulatory functions at these specialized regions of the plasma membrane. Here we describe the isolation and characterization of cDNAs encoding human and mouse zyxin. Both the human and mouse zyxin proteins display a collection of proline-rich sequences as well as three copies of the LIM domain, a zinc finger domain found in many signaling molecules. The human zyxin protein is closely related in sequence to proteins implicated in benign tumorigenesis and steroid receptor binding. Antibodies raised against human zyxin recognize an 84-kDa protein by Western immunoblot analysis. The protein is localized at focal contacts in adherent erythroleukemia cells. By Northern analysis, we show that zyxin is widely expressed in human tissues. The zyxin gene maps to human chromosome 7q32-q36.

An examination of focal adhesion formation and tyrosine phosphorylation in fibroblasts isolated from src-, fyn-, and yes- mice.

As cells adhere to extracellular matrix proteins, several focal adhesion proteins become tyrosine phosphorylated. One of the most prominent of these has been identified as the tyrosine kinase p125FAK (focal adhesion kinase, FAK). An interaction between FAK and members of the Src family tyrosine kinases p59fyn, pp60v-src, and activated pp60c-src (527F) has been demonstrated, raising the possibility that these kinases may regulate FAK activity. To explore the role of Src family kinases in focal adhesions and in the regulation of FAK activity, we isolated fibroblasts from transgenic mice that lack either pp60c-src, p59fyn, or pp62c-yes. These primary fibroblasts, and those of a control mouse, were passaged numerous times and resulted in spontaneously immortalized cell lines without the addition of transforming agents. After confirming the absence of the appropriate nonreceptor tyrosine kinases in the fyn-, src- and yes- fibroblasts, the ability of these fibroblasts to form focal adhesions and stress fibers was assessed by immunofluorescence microscopy and found to be comparable to that of normal fibroblasts. We investigated phosphotyrosine levels in response to adhesion to fibronectin and identified the pp60src substrate p130 as the one major protein with reduced levels of tyrosine phosphorylation in the cells lacking p59fyn and pp62c-yes, and particularly in those lacking pp60c-src. We examined FAK phosphorylation and kinase activity and found that there were no significant differences between these cells.

Adhesion-induced tyrosine phosphorylation of the p130 src substrate.

Adhesion of cells to the extracellular matrix leads to an increase in the tyrosine phosphorylation of a specific set of proteins, three of which have now been identified as the focal adhesion proteins pp125FAK, paxillin and tensin. In addition, we have previously noted the adhesion-induced tyrosine phosphorylation of a fourth protein, with an apparent molecular mass of 130. As in the case of FAK, paxillin and tensin, a 130 kDa protein is also found to be highly tyrosine phosphorylated in Rous sarcoma virus (RSV)-transformed cells. This protein forms a stable complex with pp60src and is directly phosphorylated by activated forms of c-src. Using a monoclonal antibody (mAb 4F4) specific for the src-associated p130 we show that p130 is also phosphorylated in response to cell adhesion. Immunoprecipitation of p130 followed by an anti-phosphotyrosine immunoblot revealed that adhesion of rat embryo fibroblasts (REF52) to fibronectin (FN) led to a significant increase in the phosphotyrosine content of p130. Furthermore, a comparison of cell lysates before and after immunoprecipitation confirmed the absence of tyrosine phosphorylated p130 from lysates immunoprecipitated with mAb 4F4. Immunofluorescence staining of REF52s revealed that p130 is found in focal adhesions as well as along stress fibers in a pattern reminiscent of that exhibited by alpha-actinin. In addition, in many cells, we found significant staining in the nucleus, but evidence is presented that the nuclear staining is not due to tyrosine phosphorylated p130. Finally, unlike pp125FAK, p130 does not appear to be itself a kinase as evidence by immune-complex kinase assays carried out in the presence or absence of exogenous substrates.

Cell spreading on extracellular matrix proteins induces tyrosine phosphorylation of tensin.

A small number of proteins becomes tyrosine-phosphorylated in response to integrin-mediated cell adhesion to extracellular matrix proteins. Previous work has identified two of these tyrosine-phosphorylated proteins as the focal adhesion kinase and paxillin. Here we identify a third focal adhesion protein, tensin, that becomes tyrosine-phosphorylated during cell adhesion to extracellular matrix proteins. The tyrosine phosphorylation of tensin does not occur when cells adhere to plastic or polylysine and is blocked when microfilament assembly and cell spreading are inhibited with cytochalasin D. In addition, we show that other focal adhesion proteins such as talin and vinculin do not become tyrosine-phosphorylated under the same conditions of cell spreading on extracellular matrix proteins.

Localization of a 215-kDa tyrosine-phosphorylated protein that cross-reacts with tensin antibodies.

Tyrosine phosphorylation of cytoskeletal proteins at adhesive junctions has been speculated to play a role in the regulation of cell signaling at these sites. Previously, monoclonal antibodies were generated against phosphotyrosine-containing proteins from Rous sarcoma virus-transformed chick embryo fibroblasts, resulting in two antibodies which recognized antigens of 76 and 215 kDa that localized to focal contacts. We have now localized the 215-kDa antigen to a number of adhesive junctions in vivo, including the zonula adherens, intercalated discs, and myotendinous and neuromuscular junctions. In sections of skeletal muscle and in isolated myofibrils, the 215-kDa protein was localized to the I-band. By immunoprecipitation and immunoblot analysis, we determined that the 215-kDa antigen cross-reacts with a polyclonal anti-tensin antibody.