title: Interaction of adipocyte fatty acid-binding protein (AFABP) and JAK2: AFABP/aP2 as a regulator of JAK2 signaling.
abstract: Adipocyte fatty acid-binding protein (AFABP/aP2) facilitates the intracellular solubilization and trafficking of lipids within the aqueous environment of the cell. Studies in the AFABP/aP2 knock-out mouse suggest that the protein may have roles in cellular processes broader than lipid transport. We present herein the finding that AFABP/aP2 interacts with JAK2 in a fatty acid-dependent manner. This interaction was established using yeast two-hybrid analysis, co-immunoprecipitation from adipose tissue, and 3T3-L1 adipocytes as well as in 293 cells overexpressing JAK2 and AFABP/aP2. Mutational analysis of AFABP/aP2 (R126L/Y128F) revealed that fatty acid binding activity is necessary for the interaction and that Asp(18) of the helix-turn-helix motif forms a component of the interaction domain. Mutational analysis of JAK2 (Y1007F/Y1008F) revealed that AFABP/aP2 associates with the basal unphosphorylated form of the protein. Interleukin-6, but not interleukin-10, stimulated phosphorylation of STAT3, and induction of SOCS3 mRNA expression were potentiated in a time- and dose-dependent manner in macrophage cell lines derived from AFABP/aP2-EFABP/mal1 double knock-out mice relative to cells from wild type animals. These results suggest that ligand-bound AFABP/aP2 binds to and attenuates JAK2 signaling and establishes a new role for AFABP/aP2 as a fatty acid sensor affecting cellular metabolism via protein-protein interactions.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Thompson
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Mazurkiewicz-Muñoz
authors.affiliation: Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, Kentucky 40292.
authors.forename: Jill
authors.initials: J
authors.lastname: Suttles
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109.
authors.forename: Christin
authors.initials: C
authors.lastname: Carter-Su
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455. Electronic address: Bernl001@umn.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Bernlohr