||PAS kinase (PASK) is an evolutionary conserved serine/threonine kinase that appears to have a role in the regulation of cellular energy metabolism. It has previously been shown that mice lacking PASK (PASK"/_ mice) are resistant to the development of hepatic steatosis (lipid accumulation in the liver), glucose intolerance, insulin resistance and obesity when placed on a high fat diet. These results suggest that PASK could be a potential target for the treatment of type II diabetes and obesity, However, the function of PASK at the cellular level is unknown. The aim of this project is to identify substrates and/or interacting partners for PASK in order to better understand its biological significance and connection to metabolic diseases. In order to achieve this objective, FLAG and HA dually-tagged constructs expressing wild type (WT) or kinase inactive (KI) PASK were generated in a viral expression vector. HepG2 cells were then infected with viral particles encoding Nterminally tagged WT or N-terminally tagged KI PASK. Tandem affinity purification (TAP) was optimized for this cell line. After purification, PASK-associated proteins were identified by mass spectrometry. Thyroid hormone receptor associated protein 3 (THRAP3), a protein involved in mRNA splicing, was identified as a potential interacting protein. However, subsequent experiments failed to reproduce this interaction with PASK in co-immunoprecipitation experiments.