ADP-ribosylation factors (ARFs) are GTP-binding proteins that regulate vesicular trafficking in the ER and Golgi (and elsewhere). ARF function requires the regulated alternation between GTP-bound active and GDP-bound inactive forms. GTP binding is catalyzed by guanine nucleotide-exchange proteins (GEPs), some of which are inhibited by BFA (a drug that inhibits protein sectretion and causes reversible disintegration of Golgi cisternae) and some of which are BFA-resistant. Among the latter is the family of ~50-kDa cytohesins, the fourth member, of which was cloned and characterized by the group. Two BFA-inhibited GEPs (BIG1 and BIG2) had been purified by the group as components of ~670-kDa macromolecular complex. Subsequent cloning was followed by structure-function studies with recombinant proteins. Immunoprecipitates of endogeneous BIG1 and BIG2 from cultured cells with specific antibodies precipitated also 70-75% of the other protein. The two very similar BIGs behaved quite differently in yeast two-hybrid experiments, where BIG1 interacted with an FKBP, and BIG2 with RIa, a regulatory subunit of cyclic AMP-activated protein kinase A (PKA). FKBP13 is a member of the FK506-binding family of immunophilins that, unlike the better known FKBP12, does not bind or inhibit calcineurin. Incubation of Jurkat cells with FK506, a widely used immunosuppressive drug, increased binding of BIG1, BIG2, and ARF to Golgi and other membranes as did a structurally related agonist. No effect was seen with a structurally related antagonist,or with cyclosporin A, or rapamycin, immunosuppressants that do not act via an FKBP. These findings are consistent with the role for FKBP13 and FK506 in vesicular trafficking, influencing ARF activity through BIG1. BIG2 interaction with RIa was confirmed by co-immunoprecipitation of in vitro-translated BIG2 and Ria, as well as of the endogenous proteins from cultured Hep G2 cells. Incubation of cells with agents that raised cell cyclic AMP concentration resulted in translocation of BIG2 (and BIG1) to Golgi and other membranes. Using 28 deletion mutants of BIG2, three regions of the molecule that interacted with one or more of the four R subunits of PKA were identified. Helical wheel projections of the sequences revealed potential amphipathic helical structures characteristic of AKAPs (A kinase-anchoring proteins). The broad spectrum of signalling events controlled by cyclic AMP requires compartmentalization of PKA and its substrate(s) along with the other molecules that are involved in specific intracellular functions. These findings are consistent with a role for BIG2 in coordinating cAMP and ARF regulatory pathways.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Intramural Research (Z01)
Project #
1Z01HL000627-25
Application #
6809642
Study Section
(PCCM)
Project Start
Project End
Budget Start
Budget End
Support Year
25
Fiscal Year
2003
Total Cost
Indirect Cost
Name
U.S. National Heart Lung and Blood Inst
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Puxeddu, Ermanno; Uhart, Marina; Li, Chun-Chun et al. (2009) Interaction of phosphodiesterase 3A with brefeldin A-inhibited guanine nucleotide-exchange proteins BIG1 and BIG2 and effect on ARF1 activity. Proc Natl Acad Sci U S A 106:6158-63
Citterio, Carmen; Vichi, Alessandro; Pacheco-Rodriguez, Gustavo et al. (2008) Unfolded protein response and cell death after depletion of brefeldin A-inhibited guanine nucleotide-exchange protein GBF1. Proc Natl Acad Sci U S A 105:2877-82
Kuroda, Fuminobu; Moss, Joel; Vaughan, Martha (2007) Regulation of brefeldin A-inhibited guanine nucleotide-exchange protein 1 (BIG1) and BIG2 activity via PKA and protein phosphatase 1gamma. Proc Natl Acad Sci U S A 104:3201-6
Shen, Xiaoyan; Hong, Myoung-Soon; Moss, Joel et al. (2007) BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein, is required for correct glycosylation and function of integrin beta1. Proc Natl Acad Sci U S A 104:1230-5
Islam, Aminul; Shen, Xiaoyan; Hiroi, Toyoko et al. (2007) The brefeldin A-inhibited guanine nucleotide-exchange protein, BIG2, regulates the constitutive release of TNFR1 exosome-like vesicles. J Biol Chem 282:9591-9
Li, Chun-Chun; Chiang, Tsai-Chen; Wu, Tsung-Sheng et al. (2007) ARL4D recruits cytohesin-2/ARNO to modulate actin remodeling. Mol Biol Cell 18:4420-37
Citterio, Carmen; Jones, Heather D; Pacheco-Rodriguez, Gustavo et al. (2006) Effect of protein kinase A on accumulation of brefeldin A-inhibited guanine nucleotide-exchange protein 1 (BIG1) in HepG2 cell nuclei. Proc Natl Acad Sci U S A 103:2683-8
Shen, Xiaoyan; Xu, Kai-Feng; Fan, Qingyuan et al. (2006) Association of brefeldin A-inhibited guanine nucleotide-exchange protein 2 (BIG2) with recycling endosomes during transferrin uptake. Proc Natl Acad Sci U S A 103:2635-40
Hiroi, Toyoko; Someya, Akimasa; Thompson, Walter et al. (2006) GEP100/BRAG2: activator of ADP-ribosylation factor 6 for regulation of cell adhesion and actin cytoskeleton via E-cadherin and alpha-catenin. Proc Natl Acad Sci U S A 103:10672-7
Xu, Kai-Feng; Shen, Xiaoyan; Li, Hewang et al. (2005) Interaction of BIG2, a brefeldin A-inhibited guanine nucleotide-exchange protein, with exocyst protein Exo70. Proc Natl Acad Sci U S A 102:2784-9

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