Insulin-like growth factor-1 receptor regulation in activated human T lymphocytes

OBJECTIVE: To investigate the kinetics of insulin-like growth factor-1 receptor (IGF-1R) expression in PHA-stimulated T lymphocytes. METHODS: IGF-1R protein and mRNA were detected by flow cytometry and RT-PCR respectively, between 0 and 48 h after cell activation. RESULTS: Few minutes after T lymphocytes were activated, internalization of the IGF-1R from the cell membrane was observed, achieving the lower level between 1 and 6 h and was accompanied by a reduction in its mRNA. This was followed by re-expression of IGF-1R on the cell surface and an increase in IGF-1R mRNA levels in the cytoplasm, reaching levels higher than those recorded initially after 48 h activation. CONCLUSION: This down- and up-regulation suggests that restoration of IGF-1R would be the result of receptor recycling and de novo synthesis and highlights its importance for T lymphocyte proliferation.