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Steel factor and c-kit regulate cell-matrix adhesion
1Center For Blood Research, Boston, MA 02115.
Abstract:
Steel (SI) and white spotting (W) loci encode steel factor (c-kit ligand) and the c-kit tyrosine kinase receptor, respectively. Mutations at these loci affect migration and differentiation of primordial germ cells, neural crest-derived melanoblasts, and hematopoietic cells. In these processes, cell adhesion molecules are hypothesized to be crucial. We have examined the role of steel factor and c-kit in cell-extracellular matrix adhesion using bone marrow-derived mast cells as a model system. Steel factor stimulates mast cells to bind to fibronectin and, to a lesser extent, to vitronectin, whereas interleukin-3 and interleukin-4, which are also mast cell growth factors, do not. Activation of adhesiveness is transient, occurs at concentrations of steel factor 100-fold lower than required for growth stimulation, and requires the integrin VLA-5. Mast cells from c-kit mutant mice adhere to fibronectin on stimulation with phorbol 12-myristate 13-acetate (PMA), but not on stimulation with steel factor, indicating that stimulation of integrin adhesiveness requires activation of the c-kit protein tyrosine kinase. By contrast, c-kit mutant and wild-type mast cells adhere equally well to COS cells expressing membrane-anchored steel factor, showing that the kinase activity of c-kit is not required for adhesion directly mediated by c-kit. Our findings suggest that regulation of adhesion is an important biologic function of steel factor.
Insights
Steel factor regulates cell adhesion by stimulating mast cells to bind fibronectin, a process dependent on the c-kit tyrosine kinase. This highlights steel factor's role in cell adhesion.
Area of Science:
- Cell Biology
- Hematology
- Developmental Biology
Background:
- The Steel (SI) and white spotting (W) loci encode key signaling molecules involved in cell development and migration.
- Steel factor (c-kit ligand) and c-kit (tyrosine kinase receptor) are crucial for primordial germ cells, melanoblasts, and hematopoietic cells.
- Cell adhesion molecules are hypothesized to play a critical role in these developmental processes.
Purpose of the Study:
- To investigate the role of steel factor and c-kit in cell-extracellular matrix adhesion.
- To utilize bone marrow-derived mast cells as a model system for studying adhesion mechanisms.
Main Methods:
- Examined mast cell adhesion to fibronectin and vitronectin.
- Utilized mast cells from c-kit mutant mice.
- Assessed adhesion in response to steel factor, interleukin-3, and interleukin-4.
- Investigated the role of integrin VLA-5 and c-kit tyrosine kinase activity.
Main Results:
- Steel factor stimulates mast cell binding to fibronectin and vitronectin, unlike IL-3 and IL-4.
- Adhesiveness activation is transient, occurs at low steel factor concentrations, and requires integrin VLA-5.
- Mast cells from c-kit mutant mice adhere to fibronectin with PMA but not steel factor, indicating c-kit kinase activation is necessary.
- C-kit kinase activity is not required for direct adhesion mediated by c-kit.
Conclusions:
- Regulation of cell adhesion is a significant biological function of steel factor.
- Steel factor signaling through c-kit tyrosine kinase modulates mast cell adhesion to the extracellular matrix.
- These findings provide insight into the molecular mechanisms governing cell migration and differentiation.