GRAP (GRB2-related adaptor protein) is a conserved adaptor protein that couples receptor and cytoplasmic tyrosine kinase signaling to the Ras/ERK MAP kinase pathway 1. The protein contains SH2 and SH3 domains characteristic of the GRB2 family 2, which enable phosphotyrosine binding and recruitment of downstream signaling molecules. In human B cells, GRAP amplifies BCR-induced ITAM signaling and connects it to Ras-controlled Erk activation, functioning largely independently of phospholipase C-γ activity 1. Critically, GRAP plays an essential role in auditory function. The protein is expressed in mouse inner ear neuronal fibers innervating cochlear and utricular hair cells 3. Loss of the Drosophila GRAP homolog (drk) in the hearing organ causes scolopidium abnormalities and deficits in negative geotaxis behavior, defects suppressible by wild-type but not mutant human GRAP 3. GRAP mutations (c.311A>T; p.Gln104Leu) cosegregate with autosomal recessive nonsyndromic deafness (DFNB114), establishing a causative link 3. Additionally, GRAP is implicated in pulmonary arterial hypertension, where m6A-modified GRAP mRNA is upregulated but protein is downregulated; GRAP overexpression alleviates HPASMC proliferation through Ras/ERK inhibition 4.