Involved in negative regulation of the TOR signaling pathway in response to type of available nitrogen source. Indirectly activates the PP2A phosphatase SIT4 via interaction with its suppressor TAP42. This interaction is enhanced under nitrogen limitation conditions. Also has a role in regulation of NPR1 in response to nitrogen limitation. Interacts with TAP42 and NPR1. Phosphorylation. Dephosphorylated by SIT4. Belongs to the TIP41 family.