Disease relevance of GBF1

• Taken together, our data demonstrate that the activity of the enterovirus 3A protein to inhibit GBF1-dependent COP-I recruitment is unique among the picornaviruses [1].

High impact information on GBF1

• Hexahistidine-tagged-GBF1 exhibited BFA-resistant guanine nucleotide exchange activity that appears specific towards ARF5 at physiological Mg2+concentration [2].
• Characterization of cDNAs recovered from the mutant and wild-type parental lines established that transcripts in these cells had identical sequence and, therefore, that GBF1 was naturally BFA resistant [2].
• Expression cloning from a cDNA library prepared from a mutant CHO cell line with Golgi-specific resistance to Brefeldin A (BFA) identified a novel 206-kD protein with a Sec7 domain termed GBF1 for Golgi BFA resistance factor 1 [2].
• The mechanism of GBF1 binding to membranes is unknown [3].
• The drug brefeldin A (BFA), an uncompetitive inhibitor of the exchange reaction that binds to an Arf-GDP-Arf GEF complex, stabilizes GBF1 on Golgi membranes [3].

Biological context of GBF1

• Mutagenesis analysis indicates that the interaction is not required for targeting GBF1 or p115 to membranes [4].
• Our findings imply that the continuous recruitment of GBF1 to spatially differentiated membrane domains is required for sustained membrane remodeling that underlies membrane traffic and Golgi biogenesis [5].
• When the N-terminal residues of the HRV 3A proteins are replaced by those of CVB3 3A, chimeric proteins are produced that have gained the ability to bind GBF1 and, by consequence, to inhibit protein transport [1].
• Sequencing of genomic DNA for CHO GBF1 and analysis of the human gene established that those variations were consistent with alternate splicing events [6].

Anatomical context of GBF1

• We report that GBF1 rapidly cycles between membranes and the cytosol (t1/2 is approximately 17 +/- 1 seconds) [7].
• ADP-ribosylation factor and coatomer have been shown to rapidly cycle between membranes and cytosol, but the membrane dynamics of GBF1 are unknown [7].
• The guanine nucleotide exchange factor GBF1 activates ARF and regulates ARF/COP I dynamics at the endoplasmic reticulum (ER)-Golgi interface [7].
• These observations indicate that GBF1 is involved in the formation of COPI-coated vesicles from the cis-Golgi or the pre-Golgi intermediate compartment through activating ADP-ribosylation factors [8].
• Its mRNA transcripts are found in 17 tissues and cell lines, likely suggesting a housekeeping role for GBF1p [9].

Associations of GBF1 with chemical compounds

• Using three different approaches [expression of an inactive (E794K) GBF1 mutant, expression of the ARF1 (T31N) mutant with decreased affinity for GTP and Brefeldin A treatment], we show that GBF1 is stabilized on membranes when in a complex with ARF-GDP [7].
• The interacting domains were mapped to the proline-rich region of GBF1 and the head region of p115 [4].
• Immunofluorescence microscopy of cells treated with nocodazole or incubated at 15 degrees C has suggested that GBF1 behaves similarly to proteins recycling between the cis-Golgi and the endoplasmic reticulum [8].

Physical interactions of GBF1

• Recently, we elucidated the underlying mechanism by showing that CVB3 3A interferes with ADP-ribosylation factor 1 (Arf1)-dependent COP-I recruitment to membranes by binding and inhibiting the function of GBF1, a guanine nucleotide exchange factor that is required for the activation of Arf1 (E. Wessels et al., Dev. Cell 11:191-201, 2006) [1].

Other interactions of GBF1

• Like ARF and coatomer, GBF1 peripherally associates with membranes [7].
• The trafficking of transmembrane proteins through the existing pathway requires GBF1-mediated ARF activation and COPI recruitment [10].

Analytical, diagnostic and therapeutic context of GBF1

• Dissection of membrane dynamics of the ARF-guanine nucleotide exchange factor GBF1 [7].
• Immunoelectron microscopy has revealed that GBF1 localizes primarily to vesicular and tubular structures apposed to the cis-face of Golgi stacks and minor fractions to the Golgi stacks [8].
• These splice variants behaved like GBF1 in biological assays based on the observation that GBF1 is cytotoxic at high levels but will confer resistance to BFA when moderately overexpressed [6].

References