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Biomedical subjects

Edna Cukierman

Publications and source records attributed to Edna Cukierman.

6 recordsLinked to original sources
PubMed2003

Targeting membrane-localized focal adhesion kinase to focal adhesions: roles of tyrosine phosphorylation and SRC family kinases.

In the present study, we examined regulation of activated focal adhesion kinase localization in focal adhesions. By using focal adhesion kinase fused to an inert transmembrane anchor, we found that the focal contact targeting region within focal adhesion kinase was preserved in the membrane-targeted fusion protein. However, upon tyrosine phosphorylation, full-length focal adhesion kinase became excluded from focal adhesions. This negative regulation of localization could be abolished by mutating key amino acid residues of focal adhesion kinase shown previously to be involved in adhesion-mediated signal transduction. Hyper-phosphorylation of endogenous focal adhesion kinase induced by pervanadate resulted in a similar reduction of localization at focal adhesions. We also show here that Src family kinases are essential for the phosphorylation-dependent exclusion of focal adhesion kinase from focal adhesions. We propose here a molecular model for the tyrosine phosphorylation-dependent regulation of focal adhesion kinase organization involving Src kinases and an inhibitory phosphorylation of the C-terminal (Tyr-925) tyrosine residue.

3T3 Cells↗
PubMed2003

uPARAP/Endo180 is essential for cellular uptake of collagen and promotes fibroblast collagen adhesion.

The uptake and lysosomal degradation of collagen by fibroblasts constitute a major pathway in the turnover of connective tissue. However, the molecular mechanisms governing this pathway are poorly understood. Here, we show that the urokinase plasminogen activator receptor-associated protein (uPARAP)/Endo180, a novel mesenchymally expressed member of the macrophage mannose receptor family of endocytic receptors, is a key player in this process. Fibroblasts from mice with a targeted deletion in the uPARAP/Endo180 gene displayed a near to complete abrogation of collagen endocytosis. Furthermore, these cells had diminished initial adhesion to a range of different collagens, as well as impaired migration on fibrillar collagen. These studies identify a central function of uPARAP/Endo180 in cellular collagen interactions.

Animals↗
PubMed2003

Specific beta1 integrin site selectively regulates Akt/protein kinase B signaling via local activation of protein phosphatase 2A.

Integrin transmembrane receptors generate multiple signals, but how they mediate specific signaling is not clear. Here we test the hypothesis that particular sequences along the beta(1) integrin cytoplasmic domain may exist that are intimately related to specific integrin-mediated signaling pathways. Using systematic alanine mutagenesis of amino acids conserved between different beta integrin cytoplasmic domains, we identified the tryptophan residue at position 775 of human beta(1) integrin as specific and necessary for integrin-mediated protein kinase B/Akt survival signaling. Stable expression of a beta(1) integrin mutated at this amino acid in GD25 beta(1)-null cells resulted in reduction of Akt phosphorylation at both Ser(473) and Thr(308) activation sites. As a consequence, the cells were substantially more sensitive to serum starvation-induced apoptosis when compared with cells expressing wild type beta(1) integrin. This inactivation of Akt resulted from increased dephosphorylation by a localized active population of protein phosphatase 2A. Both Akt and protein phosphatase 2A were present in beta(1) integrin-organized cytoplasmic complexes, but the activity of this phosphatase was 2.5 times higher in the complexes organized by the mutant integrin. The mutation of Trp(775) specifically affected Akt signaling, without effects on other integrin-activated pathways including phosphoinositide 3-kinase, MAPK, JNK, and p38 nor did it influence activation of the integrin-responsive kinases focal adhesion kinase and Src. The identification of Trp(775) as a specific site for integrin-mediated Akt signaling supports the concept of specificity of signaling along the integrin cytoplasmic domain.

Amino Acid Sequence↗
PubMed2003

Cell-matrix adhesions on poly(vinyl alcohol) hydrogels.

Cell-matrix adhesions regulate cell morphology, intracellular signaling, gene expression, and phenotype. Understanding how different methods of attaching matrix proteins to substrates affect the molecular arrangement of these adhesions offers the possibility of controlling cell function and architecture. The goal of this study was to visualize and quantify the cell-matrix adhesions formed by human fibroblasts on the matrix protein fibronectin covalently attached to poly(vinyl) alcohol (PVA) hydrogels. These adhesions were then compared with the cell adhesions formed in routine cell culture on fibronectin noncovalently coated onto glass coverslips or those formed on fibronectin covalently immobilized onto glass coverslips. Cell adhesions were characterized by immunofluorescence confocal microscopy utilizing paxillin as a marker for focal adhesions and alpha(5) integrin as a marker for fibrillar adhesions. As expected, distinct focal and fibrillar adhesions were observed in routine cell culture on coverslips coated noncovalently with fibronectin. Cells cultured on fibronectin covalently linked to PVA demonstrated diminished spatial separation of paxillin and alpha(5) integrin, accompanied by a reduction in fibrillar adhesions and fibronectin fibrillogenesis. Cells on fibronectin covalently immobilized on glass displayed the strongest marker colocalization and the most complete loss of fibrillar adhesions and lack of fibrillogenesis. These results indicate that fibronectin-conjugated PVA promotes the formation of cell adhesion structures intermediate in composition between those formed on noncovalently attached and covalently immobilized fibronectin. Furthermore, they imply that bioactive polymers can selectively induce specific cell-matrix adhesions, a characteristic that may have consequences in various tissue-engineering applications.

Cell Adhesion↗
PubMed2002

Cell interactions with three-dimensional matrices.

Signaling and other cellular functions differ in three-dimensional compared with two-dimensional systems. Cell adhesion structures can evolve in vitro towards in-vivo-like adhesions with distinct biological activities. In this review, we examine recent advances in studies of interactions of fibroblasts with collagen gels and fibronectin-containing matrices that mimic in vivo three-dimensional microenvironments. These three-dimensional systems are illuminating mechanisms of cell-matrix interactions in living organisms.

Animals↗