Question: are pentax and nikon lenses interchangeable?
Answer: All mirrorless cameras can use Pentax K-mount lenses with an adapter, but with DSLRs, it's not that simple: * Nikon can't use anything except Nikon F-mount lenses, Pentax lenses can't be used (also applies to Fujifilm DSLRs), * Canon DSLRs can use Pentax lenses only in lower-end models, with APS-C sensors.