As part of the KICSTOR complex functions in the amino acid-sensing branch of the TORC1 signaling pathway. Recruits, in an amino acid-independent manner, the GATOR1 complex to the lysosomal membranes and allows 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 the KICSTOR complex mTORC1 is constitutively localized to the lysosome and activated. The KICSTOR complex is also probably involved in the regulation of mTORC1 by glucose. Part of the KICSTOR complex composed of KPTN, ITFG2, KICS2 and SZT2. SZT2 probably serves as a link between the other three proteins in the KICSTOR complex and may mediate the direct interaction with the GATOR complex via GATOR1. The KICSTOR complex interacts directly with the GATOR1 complex and most probably indirectly with the GATOR2 complex in an amino acid-independent manner. Localization to lysosomes is amino acid-independent.