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Microtubule-associated protein 1A is the fibroblast HMW MAP undergoing mitogen-stimulated serine phosphorylation
A K Erickson1, L B Ray, T W Sturgill
1Department of Medicine, University of Virginia School of Medicine, Charlottesville 22908.
Abstract:
A variety of antibodies to microtubule-associated protein (MAP) have been used to demonstrate that phosphorylation of a 350 kDa microtubule-associated protein is stimulated 2-3 fold by epidermal growth factor or serum in quiescent 3T3-L1 fibroblasts and by insulin in 3T3-L1 adipocytes. Phosphorylation occurs on serine residues, and is maximal by 15-20 min. The phosphoprotein has been identified as MAP1A by specific immunoprecipitation with a well-characterized monoclonal antibody.
Insights
Epidermal growth factor, serum, and insulin stimulate the phosphorylation of a specific microtubule-associated protein (MAP). This protein, identified as MAP1A, undergoes serine phosphorylation in response to these growth factors.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Microtubule-associated proteins (MAPs) play crucial roles in microtubule dynamics.
- Growth factors and hormones are known regulators of cellular processes, including protein phosphorylation.
Purpose of the Study:
- To investigate the effect of growth factors and hormones on microtubule-associated protein phosphorylation.
- To identify the specific MAP involved and the nature of its modification.
Main Methods:
- Utilized antibodies against microtubule-associated proteins (MAPs).
- Employed immunoprecipitation with a monoclonal antibody to identify the phosphoprotein.
- Analyzed phosphorylation on serine residues.
Main Results:
- Phosphorylation of a 350 kDa MAP was stimulated 2-3 fold by epidermal growth factor or serum in fibroblasts.
- Insulin stimulated the same phosphorylation in adipocytes.
- Phosphorylation occurred on serine residues, peaking within 15-20 minutes.
- The phosphoprotein was identified as MAP1A.
Conclusions:
- MAP1A is a target for growth factor and insulin signaling pathways.
- MAP1A phosphorylation is a rapid cellular response to specific extracellular stimuli.
- This phosphorylation event involves serine residues and is cell-type specific depending on the stimulus.