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Prolonged activation of ERK2 by epidermal growth factor and other growth factors requires a functional insulin-like
1Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Abstract:
We have investigated the activation of ERK2, a serine/threonine kinase necessary for transmission of mitogenic signals, in cells derived from mouse embryos homozygous for a null mutation of the insulin-like growth factor (IGF)-1R gene (R- cells) and from wild-type littermates (W cells), respectively. Stimulation of quiescent W cells with IGF-1, epidermal growth factor (EGF), or with a combination growth factors induced both a maximal transient and a prolonged activation of ERK2, whereas platelet-derived growth factor or a combination of platelet-derived growth factor and EGF resulted only in transient activation of ERK2. In contrast, stimulation of R cells with IGF-1, EGF, or combinations of growth factors resulted in a transient and submaximal activation of ERK2. Reintroduction of a wild-type human IGF-1R or of a C-terminus IGF-1R mutant, but not of a juxtamembrane mutant IGF-1R, into R- cells was able to restore ERK2 activation to wild-type levels. Thus, prolonged ERK2 activation in mouse embryo fibroblasts stimulated with purified growth factors is largely dependent on a signal generated by the IGF-1R.
Insights
Prolonged activation of ERK2, crucial for cell growth signals, relies heavily on the insulin-like growth factor 1 receptor (IGF-1R). This finding highlights IGF-1R
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Signal transduction
Background:
- ERK2 (extracellular signal-regulated kinase 2) is vital for transmitting mitogenic signals.
- The insulin-like growth factor 1 receptor (IGF-1R) plays a key role in cell growth and development.
- Understanding growth factor signaling is crucial for comprehending cell proliferation and differentiation.
Purpose of the Study:
- To investigate the role of IGF-1R in ERK2 activation.
- To determine how different growth factors activate ERK2 in the presence and absence of functional IGF-1R.
- To identify specific domains of IGF-1R critical for prolonged ERK2 activation.
Main Methods:
- Utilized mouse embryo fibroblasts with and without a functional IGF-1R gene.
- Stimulated cells with various growth factors including IGF-1, EGF, and PDGF.
- Assessed ERK2 activation levels via Western blotting or similar biochemical assays.
- Restored IGF-1R function in knockout cells using wild-type and mutant IGF-1R constructs.
Main Results:
- Wild-type cells showed prolonged ERK2 activation with IGF-1 and EGF stimulation.
- Cells lacking IGF-1R exhibited only transient and submaximal ERK2 activation.
- Reintroduction of wild-type IGF-1R, but not a juxtamembrane mutant, restored prolonged ERK2 activation.
- Prolonged ERK2 activation was largely dependent on signals generated by IGF-1R.
Conclusions:
- The insulin-like growth factor 1 receptor is essential for sustained ERK2 activation in response to certain growth factors.
- Specific domains within the IGF-1R are critical for mediating prolonged ERK2 signaling.
- This study elucidates a key mechanism by which IGF-1R regulates mitogenic signaling pathways.