ARF-GEP(100), a guanine nucleotide-exchange protein for ADP-ribosylation factor 6.
A human cDNA encoding an 841-aa guanine nucleotide-exchange protein (GEP) for ADP-ribosylation factors (ARFs), named ARF-GEP(100), which contains a Sec7 domain, a pleckstrin homology (PH)-like domain, and an incomplete IQ-motif, was identified. On Northern blot analysis of human tissues, a approximately 8-kb mRNA that hybridized with an ARF-GEP(100) cDNA was abundant in peripheral blood leukocytes, brain, and spleen. ARF-GEP(100) accelerated [(35)S]GTPgammaS binding to ARF1 (class I) and ARF5 (class II) 2- to 3-fold, and to ARF6 (class III) ca. 12-fold. The ARF-GEP(100) Sec7 domain contains Asp(543) and Met(555), corresponding to residues associated with sensitivity to the inhibitory effect of the fungal metabolite brefeldin A (BFA) in yeast Sec7, but also Phe(535) and Ala(536), associated with BFA-insensitivity. The PH-like domain differs greatly from those of other ARF GEPs in regions involved in phospholipid binding. Consistent with its structure, ARF-GEP(100) activity was not affected by BFA or phospholipids. After subcellular fractionation of cultured T98G human glioblastoma cells, ARF6 was almost entirely in the crude membrane fraction, whereas ARF-GEP(100), a 100-kDa protein detected with antipeptide antibodies, was cytosolic. On immunofluorescence microscopy, both proteins had a punctate pattern of distribution throughout the cells, with apparent colocalization only in peripheral areas. The coarse punctate distribution of EEA-1 in regions nearer the nucleus appeared to coincide with that of ARF-GEP(100) in those areas. No similar coincidence of ARF-GEP(100) with AP-1, AP-2, catenin, LAMP-1, or 58K was observed. The new human BFA-insensitive GEP may function with ARF6 in specific endocytic processes.
Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA. someyaa@nih.gov
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Someya
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Sata
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Takeda
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Pacheco-Rodriguez
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Ferrans
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Moss
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Vaughan
D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002460:Cell Line; D017931:DNA Primers; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018411:Spodoptera; D013347:Subcellular Fractions / Q000378:metabolism
D000089982:ADP-Ribosylation Factor 6; D002147:Calmodulin; D017931:DNA Primers; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; C504483:IQSEC1 protein, human; D010743:Phospholipids; D012333:RNA, Messenger; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; D002118:Calcium