Interaction of Adipocyte Fatty Acid-binding Protein (AFABP) and JAK2

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 Asp18 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. 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 Asp18 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. Obesity is a key component of the metabolic syndrome linking insulin resistance, dyslipidemia, and hypertension. This clustering of metabolic states is recognized as a major risk factor for the development of type 2 diabetes and atherosclerosis (1Flier J.S. Cell. 2004; 116: 337-350Abstract Full Text Full Text PDF PubMed Scopus (956) Google Scholar, 2Grundy S.M. Arterioscler. Thromb. Vasc. Biol. 2008; 28: 629-636Crossref PubMed Scopus (1095) Google Scholar). Adipocyte fatty acid-binding protein, AFABP/aP2, 2The abbreviations used are: AFABP/aP2, adipocyte fatty acid-binding protein; HSL, hormone-sensitive lipase; JAK2, Janus kinase 2; STAT, signal transducer and activator of transcription; IL-6, interleukin 6; IL-10, interleukin 10; BSA, bovine serum albumin; EFABP/mal1, epithelial FABP; DKO, AFABP/ap2-EFABP/mal1 double knockout; SOCS3, suppressor of cytokine signaling 3; SHP-2, Src homology containing tyrosine phosphatase 2. knock-out animals are resistant to diet-induced and molecular genetic models of insulin resistance and atherosclerosis, whereas transgenic over expression models demonstrate potentiated characteristics (3Coe N.R. Simpson M.A. Bernlohr D.A. J. Lipid Res. 1999; 40: 967-972Abstract Full Text Full Text PDF PubMed Google Scholar, 4Hertzel A.V. Bennaars-Eiden A. Bernlohr D.A. J. Lipid Res. 2002; 43: 2105-2111Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar, 5Hertzel A.V. Smith L.A. Berg A.H. Cline G.W. Shulman G.I. Scherer P.E. Bernlohr D.A. Am. J. Physiol. Endocrinol. Metab. 2006; 290: 814-823Crossref PubMed Scopus (93) Google Scholar, 6Hotamisligil G.S. Johnson R.S. Distel R.J. Ellis R. Papaioannou V.E. Spiegelman B.M. Science. 1996; 274: 1377-1379Crossref PubMed Scopus (655) Google Scholar, 7Makowski L. Boord J.B. Maeda K. Babaev V.R. Uysal K.T. Morgan M.A. Parker R.A. Suttles J. Fazio S. Hotamisligil G.S. Linton M.F. Nat. Med. 2001; 7: 699-705Crossref PubMed Scopus (572) Google Scholar, 8Baar R.A. Dingfelder C.S. Smith L.A. Bernlohr D.A. Wu C. Lange A.J. Parks E.J. Am. J. Physiol. Endocrinol. Metab. 2005; 288: 187-193Crossref PubMed Scopus (94) Google Scholar). The molecular mechanisms that underlie this phenotype have yet to be elucidated but may be due to indirect effects and the availability of lipid ligands for peroxisome proliferator receptor γ or direct effects on AFABP/aP2 interaction with cellular proteins (9Jenkins-Kruchten A.E. Bennaars-Eiden A. Ross J.R. Shen W.J. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2003; 278: 47636-47643Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar, 10Smith A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar, 11Makowski L. Brittingham K.C. Reynolds J.M. Suttles J. Hotamisligil G.S. J. Biol. Chem. 2005; 280: 12888-12895Abstract Full Text Full Text PDF PubMed Scopus (310) Google Scholar). AFABP/aP2 is a member of the cytoplasmic fatty acid-binding protein multigene family (12Hertzel A.V. Bernlohr D.A. Trends Endocrinol. Metab. 2000; 11: 175-180Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar). FABPs are low molecular mass 15-kDa cytoplasmic proteins that bind fatty acids with high affinity in a 1:1 complex within an interior ligand binding domain (12Hertzel A.V. Bernlohr D.A. Trends Endocrinol. Metab. 2000; 11: 175-180Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar). They function to solubilize and traffic fatty acids throughout the aqueous cellular environment, thereby increasing the diffusion of molecules between cellular compartments. The family members have 20–70% sequence identity yet maintain super-imposable crystal structures and similar fatty acid affinity and specificity. Fatty acid binding leads to defined, but subtle changes in the protein structure including alterations in the side chain of Phe57 and the orientation of the helix-turn-helix domain (including amino acids Asp-Tyr-Met-Lys21) that caps the lipid binding pocket. The divergent sequence among members confers subtle differences in ligand binding properties between the family members but may also define different protein-protein interaction partners depending upon the cellular context. Indeed, it has been shown that the adipocyte, epithelial, and heart type fatty acid-binding proteins interact with hormone-sensitive lipase, whereas the intestinal and liver isoforms do not (9Jenkins-Kruchten A.E. Bennaars-Eiden A. Ross J.R. Shen W.J. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2003; 278: 47636-47643Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar, 10Smith A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar). AFABP/aP2 is highly expressed in adipocytes and macrophages and has a role in lipid metabolism in both cell types. In adipocytes, AFABP/aP2 has no role in fatty acid influx but mediates lipolysis and lipid re-esterification that in turn affect glucose metabolism (3Coe N.R. Simpson M.A. Bernlohr D.A. J. Lipid Res. 1999; 40: 967-972Abstract Full Text Full Text PDF PubMed Google Scholar, 5Hertzel A.V. Smith L.A. Berg A.H. Cline G.W. Shulman G.I. Scherer P.E. Bernlohr D.A. Am. J. Physiol. Endocrinol. Metab. 2006; 290: 814-823Crossref PubMed Scopus (93) Google Scholar, 6Hotamisligil G.S. Johnson R.S. Distel R.J. Ellis R. Papaioannou V.E. Spiegelman B.M. Science. 1996; 274: 1377-1379Crossref PubMed Scopus (655) Google Scholar, 8Baar R.A. Dingfelder C.S. Smith L.A. Bernlohr D.A. Wu C. Lange A.J. Parks E.J. Am. J. Physiol. Endocrinol. Metab. 2005; 288: 187-193Crossref PubMed Scopus (94) Google Scholar). In macrophages, the role of AFABP/aP2 in lipid metabolism is undefined, but studies in null macrophages reveal a role in cholesterol metabolism and inflammation (11Makowski L. Brittingham K.C. Reynolds J.M. Suttles J. Hotamisligil G.S. J. Biol. Chem. 2005; 280: 12888-12895Abstract Full Text Full Text PDF PubMed Scopus (310) Google Scholar, 14Boord J.B. Maeda K. Makowski L. Babaev V.R. Fazio S. Linton M.F. Hotamisligil G.S. Arterioscler. Thromb. Vasc. Biol. 2002; 22: 1686-1691Crossref PubMed Scopus (155) Google Scholar, 15Boord J.B. Maeda K. Makowski L. Babaev V.R. Fazio S. Linton M.F. Hotamisligil G.S. Circulation. 2004; 110: 1492-1498Crossref PubMed Scopus (168) Google Scholar). The sum total of effects in adipose tissue results in changes in insulin sensitivity and atherosclerosis (3Coe N.R. Simpson M.A. Bernlohr D.A. J. Lipid Res. 1999; 40: 967-972Abstract Full Text Full Text PDF PubMed Google Scholar, 5Hertzel A.V. Smith L.A. Berg A.H. Cline G.W. Shulman G.I. Scherer P.E. Bernlohr D.A. Am. J. Physiol. Endocrinol. Metab. 2006; 290: 814-823Crossref PubMed Scopus (93) Google Scholar, 6Hotamisligil G.S. Johnson R.S. Distel R.J. Ellis R. Papaioannou V.E. Spiegelman B.M. Science. 1996; 274: 1377-1379Crossref PubMed Scopus (655) Google Scholar, 7Makowski L. Boord J.B. Maeda K. Babaev V.R. Uysal K.T. Morgan M.A. Parker R.A. Suttles J. Fazio S. Hotamisligil G.S. Linton M.F. Nat. Med. 2001; 7: 699-705Crossref PubMed Scopus (572) Google Scholar, 14Boord J.B. Maeda K. Makowski L. Babaev V.R. Fazio S. Linton M.F. Hotamisligil G.S. Arterioscler. Thromb. Vasc. Biol. 2002; 22: 1686-1691Crossref PubMed Scopus (155) Google Scholar, 15Boord J.B. Maeda K. Makowski L. Babaev V.R. Fazio S. Linton M.F. Hotamisligil G.S. Circulation. 2004; 110: 1492-1498Crossref PubMed Scopus (168) Google Scholar, 16Maeda K. Cao H. Kono K. Gorgun C.Z. Furuhashi M. Uysal K.T. Cao Q. Atsumi G. Malone H. Krishnan B. Minokoshi Y. Kahn B.B. Parker R.A. Hotamisligil G.S. Cell Metab. 2005; 1: 107-119Abstract Full Text Full Text PDF PubMed Scopus (384) Google Scholar). The complex nature of the biological effects revealed by the knock-out models suggests a role for AFABP/aP2 in cellular processes other than lipid transport. To that end, yeast two-hybrid analysis followed by a combination of studies including titration microcalorimetry, fluorescence resonance energy transfer, and glutathione S-transferase pulldown assays have revealed that AFABP/aP2 interacts with a domain on hormone-sensitive lipase (HSL) defined by amino acid residues 190–200 containing the core sequence motif EXYK (9Jenkins-Kruchten A.E. Bennaars-Eiden A. Ross J.R. Shen W.J. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2003; 278: 47636-47643Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar, 17Shen W.J. Liang Y. Hong R. Patel S. K. A. Bernlohr D.A. Kraemer F.B. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, W.J. K. Bernlohr D.A. Kraemer F.B. S. A. 1999; PubMed Scopus Google Scholar, A.J. Sanders M.A. C. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, A.J. Sanders M.A. Bernlohr D.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In AFABP/aP2 has a similar sequence in the helix-turn-helix that is necessary for the interaction with A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar). We a protein-protein interaction between AFABP/aP2 and JAK2 is of a family of a role in signal from ligands that bind to members of the cytokine receptor ligand or of the is and the receptor and signaling molecules as the signal and of family or proteins J. J. C. 2000; PubMed Scopus Google Scholar, Science. PubMed Scopus Google Scholar). JAK2 has phosphorylation of have been as and 2 of and are for of JAK2 H. A. C. Cell. Biol. 2004; PubMed Scopus Google Scholar, J. Cell. Biol. PubMed Scopus Google Scholar, J. Y. Res. 2004; PubMed Scopus Google Scholar). In of have the interaction of JAK2 and AFABP/aP2. that the in AFABP/aP2 is for this interaction and may a protein-protein interaction domain for and tissue were from acid was from for and JAK2 were from Cell for total were from and and were from and were from for and were from of other were from The of and of used for in the AFABP/aP2 JAK2 binding were in the of or using the of The were as JAK2, JAK2, JAK2, AFABP/aP2, AFABP/aP2, yeast two-hybrid with JAK2 was as L. K. C. Cell. Biol. PubMed Google Scholar). was used as with a adipose as the of cells fatty acid protein and were used and A.J. Sanders M.A. C. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). of of and of were used for were with bovine serum containing cells were in and was with in of for The was with of for The cells were in and in containing and phosphatase The cell was for The cell was for to cellular The was used for and and of JAK2 was using C. serum was used as the the as the JAK2 were with protein a for 2 were in and on the to a new of and of were used to the and this was for were on were to and in for were in BSA, with in were for in in were in and and in was used for and JAK2, AFABP/aP2, and total were on the macrophages were stimulated with the cytokine for the and in the of bovine AFABP/aP2, STAT3, and were on the cell lines were established by of from wild type and AFABP/aP2-EFABP/mal1 double knock-out mice J.M. Q. Brittingham K.C. Y. M. Gorgun C.Z. Hotamisligil G.S. Suttles J. J. PubMed Scopus Google using L. PubMed Scopus Google Scholar, G.W. Suttles J. 2000; PubMed Scopus Google Scholar). of was by was from macrophages using to was with to and was using and were used to used to and mRNA are as and were using SOCS3, and and studies using a yeast two-hybrid AFABP/aP2 as an interaction with the W.J. K. Bernlohr D.A. Kraemer F.B. S. A. 1999; PubMed Scopus Google Scholar). a similar in the of AFABP/aP2 as an interaction not To this interaction in co-immunoprecipitation JAK2 was from adipose tissue of mice or from 3T3-L1 adipocytes and for AFABP/aP2, was with not reveal complex AFABP/aP2 interacts with a domain on containing the core sequence W.J. Liang Y. Hong R. Patel S. K. A. Bernlohr D.A. Kraemer F.B. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). of JAK2 and AFABP/aP2 amino acid revealed a similar sequence present in both proteins resonance energy analysis has that Asp18 of AFABP/aP2 forms a with of as a key component of the interaction domain A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar). In this JAK2 may interact with AFABP/aP2 between amino acids of the EXYK domain. studies that the interaction of AFABP/aP2 with is fatty acid-dependent (9Jenkins-Kruchten A.E. Bennaars-Eiden A. Ross J.R. Shen W.J. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2003; 278: 47636-47643Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar, A.J. Sanders M.A. Bernlohr D.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and that the orientation of the side chain of Asp18 is upon ligand binding Bernlohr D.A. PubMed Scopus Google Scholar, Bernlohr D.A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). that in protein-protein interaction assays or high to and that fatty acids from the binding of AFABP/aP2, analysis to protein-protein interactions. a to to the interactions. To the AFABP/aP2 interaction with JAK2, cells are cells fatty acid protein and and have the of fatty acid and to the interaction in an cell in the of AFABP/aP2 A.J. Sanders M.A. C. Kraemer F.B. Bernlohr D.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). overexpressing AFABP/aP2 and JAK2 were in and and cell were used for shown in wild type AFABP/aP2 with JAK2, whereas not To the interaction is the fatty acid binding AFABP/aP2 for interaction with In AFABP/aP2, and for with the fatty acid and are for high affinity lipid Bernlohr D.A. J. Biol. Chem. Full Text PDF PubMed Google Scholar, R.S. Bernlohr D.A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). that AFABP/aP2 not with JAK2, that ligand binding to AFABP/aP2 is necessary for this The sequence between and JAK2 suggests that the EXYK domain may be for the JAK2 JAK2, is on the of the and phosphorylation of the is to J. Cell. Biol. PubMed Scopus Google Scholar). To the of phosphorylation and activity of JAK2 on the both to JAK2 tyrosine that JAK2 is shown in AFABP/aP2 with JAK2 than with wild type JAK2, that AFABP/aP2 interacts with JAK2 in the unphosphorylated To the analysis of the and of JAK2, to of and JAK2 revealed total that affect JAK2 activity in a similar manner as the that and JAK2 interact with AFABP/aP2 than wild type The sum of the in the suggests that AFABP/aP2 interacts with JAK2 in the basal and that the is to the studies have revealed that and of AFABP/aP2 on the helix-turn-helix domain were necessary for the interaction with and that of residues AFABP/aP2 to interact or with A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar). do not affect the AFABP/aP2 to bind fatty acid the ligand binding function of AFABP/aP2 from protein-protein interaction A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar). the of in the AFABP/aP2 be by of The helix-turn-helix domain also has been shown to chain and side chain alterations upon ligand a that with ligand Bernlohr D.A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). To the helix-turn-helix domain of AFABP/aP2, a Asp18 to in and to in shown in expression of AFABP/aP2 with wild type JAK2 cells followed by and revealed interaction between the that Asp18 and the helix-turn-helix domain of AFABP/aP2 are for of JAK2 total of JAK2 with the results in of AFABP/aP2 was with of JAK2, was to basal that the interaction is and that the of JAK2 is the of the of interaction on AFABP/aP2 with JAK2 is not in to the interaction of AFABP/aP2 with that of to that AFABP/aP2 interaction with no on interaction with These demonstrate that the for the interaction of AFABP/aP2 with JAK2 but are not to for of the JAK2 and that AFABP/aP2 interacts with JAK2 in the basal To the of this of macrophages from AFABP/aP2-EFABP/mal1 double knock-out mice are resistant to diet-induced insulin resistance, and atherosclerosis J.B. Maeda K. Makowski L. Babaev V.R. Fazio S. Linton M.F. Hotamisligil G.S. 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PubMed Scopus Google Scholar). used phosphorylation as an of JAK2 activity in wild type and of signaling revealed that of cells with or for in phosphorylation of phosphorylation of was potentiated in the cells with wild whereas phosphorylation of was To the JAK2 signaling via the the cytokine a and the of phosphorylation a of shown in and wild type cells phosphorylation IL-6, whereas cells were phosphorylation The sensitivity to in the cells was that AFABP/aP2 attenuates a major of this signaling In the revealed no between wild type and cells and that not affect and type and AFABP/aP2-EFABP/mal1 knock-out macrophages were with or were and protein were via and for of and total protein was on the and is as to total protein. and were on the were with similar of for of the shown in A. of for the of the shown in C. of for of the shown in The of phosphorylation by both wild type and cells stimulated phosphorylation with a to basal and cells an of the signal than that AFABP/aP2 has an on of the but not a role in the mRNA for signaling and were between wild type and macrophages not phosphorylation leads to and it of a of of the is SOCS3, the signaling R. J.R. PubMed Scopus Google Scholar, R. Y. J. R. Nat. 2003; PubMed Scopus Google Scholar, S. L. B.E. Nat. 2003; PubMed Scopus Google Scholar). To the phosphorylation of in cells has for SOCS3 in the or of shown in was a induction of SOCS3 expression in the cells with the wild type The in SOCS3 expression in to well with the These are with ligand-bound AFABP/aP2 with JAK2 in the basal and thereby effects in AFABP/aP2 is a fatty acid and diffusion of fatty acids throughout the aqueous cellular mice have revealed a role of AFABP/aP2 in insulin resistance and atherosclerosis, the molecular mechanisms to are not well The studies herein a interaction between AFABP/aP2 and The studies also define this the for fatty acids to be to AFABP/aP2, JAK2 be in the unphosphorylated and of the JAK2 binding on AFABP/aP2 to a the helix-turn-helix domain. for the interaction are revealed by the that AFABP/aP2-EFABP/mal1 knock-out macrophages potentiated JAK2 a to in that adipocytes to have the interaction between AFABP/aP2 and The was to studies of AFABP/aP2 interaction with the hormone-sensitive lipase A.J. Sanders M.A. Bernlohr D.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In studies of the lipid or of the protein-protein was key complex a were to the interaction between AFABP/aP2 and JAK2 the of the interaction due to used for co-immunoprecipitation cells are of to of JAK2 to define the of amino In this that the fatty acid binding AFABP/aP2 was to interact with The ligand of this interaction is to be the that for protein-protein interaction analysis do not for AFABP/aP2, as ligands be from the protein with used in The fatty acid AFABP/aP2 to as a of intracellular fatty acid interaction with This have major on JAK2 signaling fatty acid are Fatty acid be in the in both adipocytes and macrophages, in this AFABP/aP2 with AFABP/aP2 has a role in insulin resistance and atherosclerosis, it may be a fatty acid sensor for JAK2 signaling for has revealed that AFABP/aP2 interacts with within a sequence W.J. Liang Y. Hong R. Patel S. K. A. Bernlohr D.A. Kraemer F.B. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). The EXYK motif is also in AFABP/aP2 it an motif to studies have revealed that a of and in AFABP/aP2 is necessary for the interaction with and that a interaction from Asp18 of AFABP/aP2 to of is for this A.J. Sanders M.A. Juhlmann B.E. Hertzel A.V. Bernlohr D.A. J. Biol. Chem. 2008; 283: 33536-33543Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar). We that AFABP/aP2 interacts with a similar sequence in was with AFABP/aP2, the AFABP/aP2 no on the of results in similar ligand the that ligand binding is has This suggests that the amino acids for interaction may be different than with HSL, but the helix-turn-helix domain is for this in this domain may not be to this interaction due to other or residues for this interaction with this is the of JAK2 is in the cell as by JAK2 This has to AFABP/aP2 interaction with the basal JAK2 in for and are necessary for by this in of JAK2 J. Cell. Biol. PubMed Scopus Google Scholar). of of the residues or in in a in the total that of the affect JAK2 activity in a similar manner. AFABP/aP2 interaction with was that AFABP/aP2 interacts with JAK2 in the unphosphorylated This AFABP/aP2 to signaling by not JAK2 to or to other JAK2 protein-protein partners from be that in the cell of JAK2 is using the JAK2 and in of total AFABP/aP2 is the JAK2 total JAK2 and the of AFABP/aP2 in may AFABP/aP2 with the results that the with a fatty acid forms a that a of protein is in macrophages AFABP/aP2 is an protein, that a of AFABP/aP2 may interact with JAK2 and function as a signaling The interaction suggest that AFABP/aP2, to a fatty acid interacts with unphosphorylated To the of AFABP/aP2 on JAK2 of the AFABP/aP2-EFABP/mal1 double knock-out mice in an null have atherosclerosis on a J.B. Maeda K. Makowski L. Babaev V.R. Fazio S. Linton M.F. Hotamisligil G.S. Circulation. 2004; 110: 1492-1498Crossref PubMed Scopus (168) Google Scholar). The finding that AFABP/aP2 null an null results in a atherosclerosis, suggests that expression of FABPs in the macrophage is to atherosclerosis development L. Boord J.B. Maeda K. Babaev V.R. Uysal K.T. Morgan M.A. Parker R.A. Suttles J. Fazio S. Hotamisligil G.S. Linton M.F. Nat. Med. 2001; 7: 699-705Crossref PubMed Scopus (572) Google Scholar). of atherosclerosis is a complex between cell cytokine and and both have B. A. K. C. M. C. S. H. Circulation. 2004; 110: PubMed Scopus Google Scholar, M. B. M. S. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar, R. S. Res. 2008; PubMed Scopus Google Scholar). the phenotype of the null mice and the of JAK2 and signaling in macrophages derived from The results a in whereas signaling was in the This suggests that AFABP/aP2 has effects on JAK2 that may be due to the of other signaling Indeed, signaling and signaling do have as the of and SOCS3 as in signaling C. A. S. R. G. J. 2003; PubMed Scopus Google Scholar, G. L. J. PubMed Scopus Google Scholar, S. L. B.E. Nat. 2003; PubMed Scopus Google Scholar, J. C. S. S. A. G. J. 2004; PubMed Scopus Google Scholar, H. M. H. M. K. S. M. A. Nat. 2003; PubMed Scopus Google Scholar). analysis of other is necessary to the of the AFABP/aP2 To this end, studies using AFABP/aP2 3T3-L1 adipocytes revealed that the protein no on JAK2 signaling not JAK2 signaling is complex and from cytokine to cytokine has different in of the proteins other as protein and and as be to the that AFABP/aP2 to the necessary for of JAK2 signaling in other The of AFABP/aP2 on phosphorylation suggests that role is the of JAK2, the These results are with AFABP/aP2 JAK2 kinase activity protein-protein interactions. In a interaction between AFABP/aP2 and AFABP/aP2 interacts the helix-turn-helix domain in a manner with unphosphorylated JAK2 and results in an of a JAK2 signaling this AFABP/aP2 as a fatty acid sensor for JAK2, in the of JAK2 signaling as a of the lipid of the cell. We the members of the Bernlohr for and the development of this We for the JAK2 and throughout this We also the of