Transmembrane adapters: attractants for cytoplasmic effectors

Transmembrane adapter proteins (TRAPs) are a relatively new and growing family of proteins that include linker for activation of T cells (LAT), phosphoprotein associated with glycosphingolipid-enriched micro domains (PAG)/C-terminal Src kinase (Csk) binding protein (Cbp), SHP2-interacting transmembrane adapter protein (SIT), T cell receptor interacting molecule (TRIM), and the recently identified non-T cell activation linker (NTAL) and pp30. TRAPs share several common structural features, but more importantly they possess multiple sites of tyrosine phosphorylation, by which they act as scaffolds for recruiting cytosolic adapter and/or effector proteins. The membrane association of TRAPs places them near to the immunoreceptors, a position from which they coordinate and modulate the signals they receive to produce an appropriate cellular response.