Mammalian AMP-activated protein kinase (AMPK) is a heterotrimeric serine/threonine protein kinase that acts as a sensor of cellular energy status. It interacts with a great variety of different substrates leading to short-term (i.e. regulation of the activity of different enzymes by direct phosphorylation) and long-term effects (i.e. regulation of transcriptional activity of different transcription factors). In this work, we describe the use of the yeast two-hybrid technology to identify additional proteins that interact with the different subunits of AMPK. We have performed three yeast two-hybrid screenings of a human skeletal muscle cDNA library using three different baits: a constitutively active form of AMPKalpha2 (LexA-AMPKalpha2-T172D) co-expressed with AMPKgamma1, LexA-AMPKbeta2 and LexA-AMPKgamma3. Our results identify novel interaction partners of AMPK in human skeletal muscle. We also further characterize the interaction of AMPK with one of these novel interacting proteins, the non-ATPase subunit of the proteasome PSMD11. Our results indicate that AMPK is able to interact physically with this subunit and modify its phosphorylation status, supporting a possible role for AMPK in regulating proteasome function.