RIT and RIN are two small guanine nucleotide binding proteins that share more than 50% sequence identity with RAS, including highly conserved core effector domains. Unlike RAS, the C termini of RIT and RIN lack a typical prenylation motif (CAAX, XXCC, or CXC) required for the association of RAS proteins with the plasma membrane. RIT is expressed in all tissues, whereas RIN is neuron-specific. They have similar signalling properties and are activated by NGF through unknown exchange factors. They signal to ERKs and p38 MAP kinase. They mainly lead to p38 activation via the BRAF-MEK kinase cascade.