Reference work entry
Antigen receptor stimulation of T cells and B cells results in the rapid conversion of the small GTPase Ras from its “inactive” GDP-bound form to its “active” GTP-bound form (Alberola-Ila and Hernández-Hoyos 2003). However, the mechanisms of Ras regulation in lymphocytes, particularly by phorbol esters, had long remained a mystery as known signaling pathways could not account for its activation. The discovery of the Ras guanyl-nucleotide exchange factor RasGRP1, cloned by two groups searching for novel Ras activators in rat brain and murine T cells, was a major advance leading to a better understanding of Ras regulation in lymphocytes (Stone 2011). Ectopic expression of...
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