ADP-Ribosylation Factor

ADP-ribosylation factor-like protein 9 (ARL9) is a member of to 2 novel subfamilies coding for small GTPases that were found to be highly conserved among eukaryotes.

ARL6 is a member of the ARF family of GTP-binding proteins. ARL6 has a vital part in modulating membrane trafficking and cytoskeletal functions. Mutation in ARL6 is the source of Bardet-Biedl syndrome (BBS3) which is a pleiotropic genetic disorder that causes obesity, photoreceptor degeneration, polydactyly, hypogenitalism, renal abnor-malities and developmental delay.

ADP-ribosylation factor-like protein 5B (ARL5B) is a member of a family of proteins which are structurally similar to ADP-ribosylation factors. ARLs and ARFs belong to the RAS superfamily of regulatory GTPases. ARL5B is most closely related to ARL5, with which it shares 80% sequence identity. Furthermore, Human ARL5B shares 100% identity with mouse ARL8 and 71% identity with the Drosophila homolog.

ARL5A is a member of the ARF family of GTP-binding proteins. ARFs are vital in eukaryotic vesicular trafficking pathways and have a crucial part in the activation of phospholipase D. Different from ARF family members, ARL5 is believed to lack ADP-ribosylation enhancing activity. ARL5A is developmentally regulated and has a role in nuclear dynamics and signaling cascades during embryonic development.

ARL4D is a developmentally regulated member of the ADP-ribosylation factor/ARF-like protein (ARF/ARL) family of Ras-related GTPases. Small GTP-binding protein which cycles between an inactive GDP-bound and an active GTP-bound form, and the rate of cycling is regulated by guanine nucleotide exchange factors (GEF) and GTPase-activating proteins (GAP). ARL4D takes part in membrane-associated intracellular trafficking. Mutations in this gene is linked to Bardet-Biedl syndrome (BBS).

ARL4A is related Specifically to ARL6 and ARL7 and belongs to the ARF-like protein (ARL) subfamily of small GTPases. However, unlike ARFs, ARL4 does not activate the cholera toxin ADP-ribosyltranferase. ARL4A takes part in neurogenesis during embryonic development and somitogenesis in the early stages of adult spermatogenesis.

ARL3 (ARFL3) belongs to the ARF-like protein (ARL) subfamily of small GTPases. ARL3 does not activate the cholera toxin ADP-ribosyltranferase contrasting from ARFs. ARL3 is ubiquitously expressed. ARL3 may have a role in maintaining rod photoreceptor cells and regulating microtubule-dependent processes. ARL3 knockdown leads to altered cell morphology, failure of cytokinesis, acetylation of alpha tubulin and an increase in binucleated cells.

ARL2BP is an effector of ADP-ribosylation factor-like 2(ARL2) which is vital for nuclear retention of STAT3. The ARL2BP protein binds to ARL2.GTP with high affinity but does not interact with ARL2.GDP, activated ARF, or RHO proteins. Though primarily cytosolic, ARL2BP can enter the mitochondria and bind the adenine nucleotide transporter while bound to ARL2. Accordingly, it may also be involved in mitochondria transport and apoptosis.

ARL2 is a member of the ADP-ribosylation factor (ARF) family. ARL2 functions as a component of a secretory pathway which is involved in the Ca2-dependent release of acetylcholine. ARL2 has a role in the folding of tubule proteins, thus playing a significant role in microtubule dynamics and cell cycle progression. Unlike other members of the ARF family, ARL2 doesn’t act as an activator of the catalytic subunit of cholera toxin.

ARL15 is a member of the ARF family which are essential in eukaryotic vesicular trafficking pathways and have a vital part in the activation of phospholipase D. ARL15 variants influence levels of Acrp30, an adipocyte-derived protein that is extremely genetic and inversely related to the prospect of type 2 diabetes mellitus and coronary heart disease.

ADP-ribosylation factor-like 14 (ARL14) is a developmentally regulated member of the ADP-ribosylation factor/ARF-like protein (ARF/ARL) family of Ras-related GTPases. ARL14 is GTPase which recruits MYO1E to MHC class II-containing vesicles via the effector protein C11orf46/ARF7EP and thus controls the movement of these vesicles along the actin cytoskeleton in dendritic cells. MHC-II transport was controlled by the GTPase ARL14/ARF7, which recruits the motor myosin 1E via an effector protein ARF7EP.

ARL11 (ADP-ribosylation factor-like protein 11) belongs to the ARF family of the Ras superfamily of small GTPases which are known to be involved in multiple regulatory pathways altered in human carcinogenesis. ARFs are highly conserved guanine nucleotide binding proteins which enhance the ADP-ribosyltransferase activity of choleratoxin. ARFs are important in eukaryotic vesicular trafficking pathways and they have a vital role in the activation of phospholipase D (PC-PLD). ARL11 is assumed to act as a tumor suppressor which may have a role in the regulation of apoptosis.

ARL1 is part of the ARL (ADP-ribosylation factor-like) family of proteins, which are structurally associated to ADP-ribosylation factors (ARFs). ARFs, described as activators of cholera toxin (CT) ADP-ribosyltransferase activity, control intracellular vesicular membrane trafficking, and stimulate a phospholipase D (PLD) isoform.
ARL1 is a weak stimulator of PLD and CT in a phospholipid dependent manner.
ARL1 is a GTP-binding protein that has low efficiency as allosteric activator of the cholera toxin catalytic subunit, an ADP-ribosyltransferase. ARL1 is involved in the Golgi apparatus.

Arfaptin 2 (ARFIP2) is a Rac1 binding protein essential for Rac-mediated actin polymerization and the succeeding formation of membrane ruffles and lamellipodia. ARFIP2 is a putative target protein of ADP-ribosylation factor. ARFIP2 is also involved in membrane ruffling. ARFIP2 expression is increased at sites of neurodegeneration. In addition, ARFIP2 interacts with the ADP ribosylation factor ARF6, a GTPase which associates with the plasma membrane and intracellular endosome vesicles, in a GTP dependent mode. Furthermore, Arfaptin 2 controls the aggregation of mutant Huntingtin protein by weakening proteasome function.

ADP-Ribosylation Factor Interacting Protein 1 (ARFIP1) contains 1 AH domain and is a putative target protein of ADP-ribosylation factor.

ADP-Ribosylation Factor Interacting Protein 1 (ARFIP1) contains 1 AH domain and is a putative target protein of ADP-ribosylation factor.

ARF6 is a part of the ADP ribosylation factor family of GTP-binding proteins. ARF6 is restricted to the plasma membrane, and controls vesicular trafficking, remodeling of membrane lipids, and signaling pathways which lead to actin remodeling. Furthermore, ARF6 is a key player in conservation of organelle integrity, assembly of coat proteins and activation of phospholipase D.

ADP-ribosylation factor 5 (ARF5) is a small guanine nucleotide-binding protein which enhances the enzymatic activities of cholera toxin. ARF-dependent regulatory mechanisms include the coordination of spectrin interactions with golgi membranes and the connection of actin to the golgi via rho family-dependent G-protein localization and WASP/Arp2/3 complexes. ARF5 is involved in vesicular transport and functioning via phospholipase D activation.

ARF4 belongs to the ARF gene family whose members encode small guanine nucleotide-binding proteins which stimulate the ADP-ribosyltransferase activity of cholera toxin and have a role in vesicular trafficking and as activators of phospholipase D. The ARF proteins include five ARF proteins and eleven ARF-like proteins and constitute one family of the RAS superfamily. They are classified as class I, class II and class III; the ARF4 gene is a class II member. The members of each class share a common gene organization. The ARF4 gene spans approximately 12kb and contains 6 exons and 5 introns. The ARF4 gene is the most divergent member of the human ARFs.

ADP-ribosylation factor 3 (ARF3) belongs to the human ARF gene family. This family encodes small guanine nucleotide-binding proteins which stimulate the ADP-ribosyltransferase activity of cholera toxin and have a role in vesicular trafficking and as activators of phospholipase D. ARF3 functions as an allosteric activator of the cholera toxin catalytic subunit, an ADP-ribosyltransferase. ARF3 is involved in protein trafficking; may modulate vesicle budding and uncoating within the Golgi apparatus. The ARF3 gene is comprised of 5 exons and 4 introns.

ARF1 is a small guanine nucleotide-binding protein that increases the enzymatic activities of cholera toxin. ARF1 is necessary and ubiquitous in eukaryotes. ARF1 takes part in vesicular transport and functioning via phospholipase D activation. ARF1 is involved in membrane traffic and organelle integrity which are closely tied to their reversible association with membranes and distinct interactions with membrane phospholipids.