Exchange Factor EFA6R Requires C-terminal Targeting to the Plasma Membrane to Promote Cytoskeletal Rearrangement through the Activation of ADP-ribosylation Factor 6 (ARF6)

Kanamarlapudi, Venkateswarlu

doi:10.1074/jbc.m113.534156

Cited by 35 publications

(70 citation statements)

References 48 publications

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“…As mentioned above, the ARF6 GTPase cycle is critical for its normal function and the constitutively active ARF6-Q67L mutant disrupts rather than facilitates ARF6-dependent recycling (Cohen et al, 2007;D'Souza-Schorey et al, 1998;Donaldson, 2003;Donaldson et al, 2009;Eyster et al, 2009;Maldonado-Báez et al, 2013;Santy, 2002). Overexpression of ARF6 GEFs is commonly employed as a more physiological means to activate ARF6 (Cohen and Donaldson, 2010;Kanamarlapudi, 2014;Santy and Casanova, 2001). However, GEF overexpression can also lead to ARF6 hyperactivation, inducing abnormal, non-physiological phenotypes similarly to the ARF6-Q67L mutant (Cohen et al, 2007;Li et al, 2012;Monier et al, 1998).…”

Section: Sphingolipids Increase Internalization and Block Endosomal Rmentioning

confidence: 99%

Sphingolipids inhibit endosomal recycling of nutrient transporters by inactivating ARF6

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Ramirez

Liu

et al. 2018

Journal of Cell Science

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Endogenous sphingolipids (ceramide) and related synthetic molecules (FTY720, SH-BC-893) reduce nutrient access by decreasing cell surface expression of a subset of nutrient transporter proteins. Here, we report that these sphingolipids disrupt endocytic recycling by inactivating the small GTPase ARF6. Consistent with reported roles for ARF6 in maintaining the tubular recycling endosome, MICAL-L1-positive tubules were lost from sphingolipid-treated cells. We propose that ARF6 inactivation may occur downstream of PP2A activation since: (1) sphingolipids that fail to activate PP2A did not reduce ARF6-GTP levels; (2) a structurally unrelated PP2A activator disrupted tubular recycling endosome morphology and transporter localization; and (3) overexpression of a phosphomimetic mutant of the ARF6 GEF GRP1 prevented nutrient transporter loss. ARF6 inhibition alone was not toxic; however, the ARF6 inhibitors SecinH3 and NAV2729 dramatically enhanced the killing of cancer cells by SH-BC-893 without increasing toxicity to peripheral blood mononuclear cells, suggesting that ARF6 inactivation contributes to the anti-neoplastic actions of sphingolipids. Taken together, these studies provide mechanistic insight into how ceramide and sphingolipid-like molecules limit nutrient access and suppress tumor cell growth and survival.

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Section: Sphingolipids Increase Internalization and Block Endosomal Rmentioning

confidence: 99%

Sphingolipids inhibit endosomal recycling of nutrient transporters by inactivating ARF6

Finicle

Ramirez

Liu

et al. 2018

Journal of Cell Science

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“…Active ARF6 pull down assay ARF6 activation was assessed by using the GST-GGA3 protein binding domain (PBD; amino acids 1-316) pulldown assay (Kanamarlapudi, 2014). The GST-GGA3 PBD fusion protein purified and coupled to glutathione beads as previously described (Venkateswarlu et al, 1998).…”

Section: Preparation Of the Cell Lysatesmentioning

confidence: 99%

Luteinizing hormone/chorionic gonadotrophin receptor overexpressed in granulosa cells from polycystic ovary syndrome ovaries is functionally active

Kanamarlapudi

Gordon

Bernal

2016

Reproductive BioMedicine Online

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. AbstractPolycystic ovarian syndrome (PCOS) is associated with anovulatory infertility. Luteinizing hormone/chorionic gonadotropin receptor (LHCGR), which is critical for ovulation, has been suggested to be expressed prematurely in the ovarian follicles of women with PCOS. The objective of this study was to analyse the expression and activity of LHCGR in ovarian granulosa cells from PCOS patients and the involvement of ARF6 small GTPase in LHCGR internalisation. Granulosa cells (GCs) isolated from follicular fluid collected during oocyte retrieval from normal women (n=19) and women with PCOS (n=17) were used to study differences in LHCGR protein expression and activity between normal and PCOS patients.LHCGR expression is up-regulated in GCs from PCOS women. LHCGR in PCOS GCs is functionally active as evidenced by increased cAMP production upon human gonadotrophin (HCG)-stimulation. Moreover, ARF6 is highly expressed in GCs from PCOS patients and HCG-stimulation increases the levels of active ARF6. The inhibition of ARF6 activation attenuates HCG-induced LHCGR internalisation in both normal and PCOS GCs, indicating that there are no alterations in LHCGR internalisation in GCs from PCOS. In conclusion, the expression and activation of LHCGR and ARF6 are up-regulated in GCs from PCOS women but the mechanism of agonist-induced LHCGR internalisation is unaltered.

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“…On the other hand, human EFA6D isoform B does not correspond to any of the mouse EFA6D variants in terms of sequence similarity in the N‐terminal region, although the predicted molecular weight is similar to that of EFA6D1a. In a previous immunoblotting analysis with an antibody against the C‐terminal 15 amino acids of human EFA6D, in which 14 of 15 amino acids (93.3%) were identical to those of the mouse EFA6D1 variants, only an immunoreactive band for isoform B was detectable in the human brain (Kanamarlapudi, ). It currently remains unknown whether the patterns of alternative splicing of the EFA6D gene and functions of EFA6D variants may be species‐specific.…”

Section: Discussionmentioning

confidence: 98%

Distinct subcellular localization of alternative splicing variants of EFA6D, a guanine nucleotide exchange factor for Arf6, in the mouse brain

Fukaya

Ohta

Hara

et al. 2016

J of Comparative Neurology

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EFA6D (guanine nucleotide exchange factor for ADP-ribosylation factor 6 [Arf6]D) is also known as EFA6R, Psd3, and HCA67. It is the fourth member of the EFA6 family with guanine nucleotide exchange activity for Arf6, a small guanosine triphosphatase (GTPase) that regulates endosomal trafficking and actin cytoskeleton remodeling. We propose a classification and nomenclature of 10 EFA6D variants deposited in the GenBank database as EFA6D1a, 1b, 1c, 1d, 1s, 2a, 2b, 2c, 2d, and 2s based on the combination of N-terminal and C-terminal insertions. Polymerase chain reaction analysis showed the expression of all EFA6D variants except for variants a and d in the adult mouse brain. Immunoblotting analysis with novel variant-specific antibodies showed the endogenous expression of EFA6D1b, EFA6D1c, and EFA6D1s at the protein level, with the highest expression being EFA6D1s, in the brain. Immunoblotting analysis of forebrain subcellular fractions showed the distinct subcellular distribution of EFA6D1b/c and EFA6D1s. The immunohistochemical analysis revealed distinct but overlapping immunoreactive patterns between EFA6D1b/c and EFA6D1s in the mouse brain. In immunoelectron microscopic analyses of the hippocampal CA3 region, EFA6D1b/c was present predominantly in the mossy fiber axons of dentate granule cells, whereas EFA6D1s was present abundantly in the cell bodies, dendritic shafts, and spines of hippocampal pyramidal cells. These results provide the first anatomical evidence suggesting the functional diversity of EFA6D variants, particularly EFA6D1b/c and EFA6D1s, in neurons. J. Comp. Neurol. 524:2531-2552, 2016. © 2016 Wiley Periodicals, Inc.

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Exchange Factor EFA6R Requires C-terminal Targeting to the Plasma Membrane to Promote Cytoskeletal Rearrangement through the Activation of ADP-ribosylation Factor 6 (ARF6)

Cited by 35 publications

References 48 publications

Sphingolipids inhibit endosomal recycling of nutrient transporters by inactivating ARF6

Sphingolipids inhibit endosomal recycling of nutrient transporters by inactivating ARF6

Luteinizing hormone/chorionic gonadotrophin receptor overexpressed in granulosa cells from polycystic ovary syndrome ovaries is functionally active

Distinct subcellular localization of alternative splicing variants of EFA6D, a guanine nucleotide exchange factor for Arf6, in the mouse brain

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