KICSTOR complex protein kaptin (KPTN)

As part of the KICSTOR complex functions from the amino acid-sensing branch of this TORC1 signaling pathway. Recruits, in an amino acid-independent fashion, the GATOR1 complex to the lysosomal membranes and enables its interaction with GATOR2 and the RAG GTPases.

Functions upstream of the RAG GTPases and is required to negatively regulate mTORC1 signaling in absence of amino acids. In absence of this KICSTOR complex mTORC1 is constitutively localized to the lysosome and activated.