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Hebron KE, Perkins OL, Kim A, Jian X, Girald-Berlingeri SA, Lei H, Shern JF, Conner EA, Randazzo PA, Yohe ME. ASAP1 and ARF1 regulate myogenic differentiation in rhabdomyosarcoma by modulating TAZ activity. Mol Cancer Res 2024:749693. [PMID: 39495123 DOI: 10.1158/1541-7786.mcr-24-0490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 10/08/2024] [Accepted: 10/31/2024] [Indexed: 11/05/2024]
Abstract
Despite aggressive, multimodal therapies, the prognosis of patients with refractory or recurrent rhabdomyosarcoma (RMS) has not improved in four decades. Because RMS resembles skeletal muscle precursor cells, differentiation-inducing therapy has been proposed for patients with advanced disease. In RAS-mutant PAX fusion-negative RMS (FN-FMS) preclinical models, MEK1/2 inhibition (MEKi) induces differentiation, slows tumor growth, and extends survival. However, the response is short-lived. A better understanding of the molecular mechanisms regulating FN-RMS differentiation could improve differentiation therapy. Here, we identified a role in FN-RMS differentiation for ASAP1, an ARF GTPase-activating protein (ARF GAP) with both pro-invasive and tumor suppressor functions. We found that ASAP1 knockdown inhibited differentiation in FN-RMS cells. Interestingly, knockdown of the GTPases ARF1 or ARF5, targets of ASAP1 GAP activity, also blocked differentiation of FN-RMS. We discovered that loss of ARF pathway components blocked myogenic transcription factor expression. Therefore, we examined the effects on transcriptional regulators. MEKi led to the phosphorylation and inactivation of WWTR1 (TAZ), a homolog of the pro-proliferative transcriptional co-activator YAP1 regulated by the Hippo pathway. However, loss of ASAP1 or ARF1 blocked this inactivation, which inhibits MEKi-induced differentiation. Finally, MEKi-induced differentiation was rescued by dual knockdown of ASAP1 and WWTR1. This study shows that ASAP1 and ARF1 are necessary for myogenic differentiation, providing a deeper understanding of differentiation in FN-RMS and illuminating an opportunity to advance differentiation therapy. Implications: ASAP1 and ARF1 regulate MEKi-induced differentiation of FN-RMS cells by modulating WWTR1 (TAZ) activity, supporting YAP1/TAZ inhibition as a FN-RMS differentiation therapy strategy.
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Hammoudeh SM, Ng Y, Wei BR, Madsen TD, Yadav MP, Simpson RM, Weigert R, Randazzo PA. Tongue orthotopic xenografts to study fusion-negative rhabdomyosarcoma invasion and metastasis in live animals. CELL REPORTS METHODS 2024; 4:100802. [PMID: 38964316 PMCID: PMC11294838 DOI: 10.1016/j.crmeth.2024.100802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 04/24/2024] [Accepted: 06/05/2024] [Indexed: 07/06/2024]
Abstract
PAX3/7 fusion-negative rhabdomyosarcoma (FN-RMS) is a childhood mesodermal lineage malignancy with a poor prognosis for metastatic or relapsed cases. Limited understanding of advanced FN-RMS is partially attributed to the absence of sequential invasion and dissemination events and the challenge in studying cell behavior, using, for example, non-invasive intravital microscopy (IVM), in currently used xenograft models. Here, we developed an orthotopic tongue xenograft model of FN-RMS to study cell behavior and the molecular basis of invasion and metastasis using IVM. FN-RMS cells are retained in the tongue and invade locally into muscle mysial spaces and vascular lumen, with evidence of hematogenous dissemination to the lungs and lymphatic dissemination to lymph nodes. Using IVM of tongue xenografts reveals shifts in cellular phenotype, migration to blood and lymphatic vessels, and lymphatic intravasation. Insight from this model into tumor invasion and metastasis at the tissue, cellular, and subcellular level can guide new therapeutic avenues for advanced FN-RMS.
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Rosenberg EM, Jian X, Soubias O, Jackson RA, Gladu E, Andersen E, Esser L, Sodt AJ, Xia D, Byrd RA, Randazzo PA. Point mutations in Arf1 reveal cooperative effects of the N-terminal extension and myristate for GTPase-activating protein catalytic activity. PLoS One 2024; 19:e0295103. [PMID: 38574162 PMCID: PMC10994351 DOI: 10.1371/journal.pone.0295103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 03/05/2024] [Indexed: 04/06/2024] Open
Abstract
The ADP-ribosylation factors (Arfs) constitute a family of small GTPases within the Ras superfamily, with a distinguishing structural feature of a hypervariable N-terminal extension of the G domain modified with myristate. Arf proteins, including Arf1, have roles in membrane trafficking and cytoskeletal dynamics. While screening for Arf1:small molecule co-crystals, we serendipitously solved the crystal structure of the non-myristoylated engineered mutation [L8K]Arf1 in complex with a GDP analogue. Like wild-type (WT) non-myristoylated Arf1•GDP, we observed that [L8K]Arf1 exhibited an N-terminal helix that occludes the hydrophobic cavity that is occupied by the myristoyl group in the GDP-bound state of the native protein. However, the helices were offset from one another due to the L8K mutation, with a significant change in position of the hinge region connecting the N-terminus to the G domain. Hypothesizing that the observed effects on behavior of the N-terminus affects interaction with regulatory proteins, we mutated two hydrophobic residues to examine the role of the N-terminal extension for interaction with guanine nucleotide exchange factors (GEFs) and GTPase Activating Proteins (GAPs. Different than previous studies, all mutations were examined in the context of myristoylated Arf. Mutations had little or no effect on spontaneous or GEF-catalyzed guanine nucleotide exchange but did affect interaction with GAPs. [F13A]myrArf1 was less than 1/2500, 1/1500, and 1/200 efficient as substrate for the GAPs ASAP1, ARAP1 and AGAP1; however, [L8A/F13A]myrArf1 was similar to WT myrArf1. Using molecular dynamics simulations, the effect of the mutations on forming alpha helices adjacent to a membrane surface was examined, yet no differences were detected. The results indicate that lipid modifications of GTPases and consequent anchoring to a membrane influences protein function beyond simple membrane localization. Hypothetical mechanisms are discussed.
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Zhang Y, Soubias O, Pant S, Heinrich F, Vogel A, Li J, Li Y, Clifton LA, Daum S, Bacia K, Huster D, Randazzo PA, Lösche M, Tajkhorshid E, Byrd RA. Myr-Arf1 conformational flexibility at the membrane surface sheds light on the interactions with ArfGAP ASAP1. Nat Commun 2023; 14:7570. [PMID: 37989735 PMCID: PMC10663523 DOI: 10.1038/s41467-023-43008-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 10/30/2023] [Indexed: 11/23/2023] Open
Abstract
ADP-ribosylation factor 1 (Arf1) interacts with multiple cellular partners and membranes to regulate intracellular traffic, organelle structure and actin dynamics. Defining the dynamic conformational landscape of Arf1 in its active form, when bound to the membrane, is of high functional relevance and key to understanding how Arf1 can alter diverse cellular processes. Through concerted application of nuclear magnetic resonance (NMR), neutron reflectometry (NR) and molecular dynamics (MD) simulations, we show that, while Arf1 is anchored to the membrane through its N-terminal myristoylated amphipathic helix, the G domain explores a large conformational space, existing in a dynamic equilibrium between membrane-associated and membrane-distal conformations. These configurational dynamics expose different interfaces for interaction with effectors. Interaction with the Pleckstrin homology domain of ASAP1, an Arf-GTPase activating protein (ArfGAP), restricts motions of the G domain to lock it in what seems to be a conformation exposing functionally relevant regions.
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Hammoudeh SM, Ng Y, Wei BR, Madsen TD, Simpson RM, Weigert R, Randazzo PA. Fusion-negative rhabdomyosarcoma orthotopic tongue xenografts for study of invasion, intravasation and metastasis in live animals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.21.558858. [PMID: 38076999 PMCID: PMC10705524 DOI: 10.1101/2023.09.21.558858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
PAX3/7 Fusion-negative rhabdomyosarcoma (FN-RMS) is a childhood mesodermal lineage malignancy with a poor prognosis for metastatic or relapsed cases. Towards achieving a more complete understanding of advanced FN-RMS, we developed an orthotopic tongue xenograft model for studies of molecular basis of FN-RMS invasion and metastasis. The behavior of FN-RMS cells injected into murine tongue was examined using in vivo bioluminescence imaging, non-invasive intravital microscopy (IVM), and histopathology and compared to the prevailing hindlimb intramuscular and subcutaneous xenografts. FN-RMS cells were retained in the tongue and invaded locally into muscle mysial spaces and vascular lumen. While evidence of hematogenous dissemination to the lungs occurred in tongue and intramuscular xenografts, evidence of local invasion and lymphatic dissemination to lymph nodes only occurred in tongue xenografts. IVM and RNA-seq of tongue xenografts reveal shifts in cellular phenotype and differentiation state in tongue xenografts. IVM also shows homing to blood and lymphatic vessels, lymphatic intravasation, and dynamic membrane protrusions. Based on these findings, the tongue orthotopic xenograft of FN-RMS is a valuable model for tumor progression studies at the tissue, cellular and subcellular levels providing insight into kinetics and molecular bases of tumor invasion and metastasis and, hence, new therapeutic avenues for advanced FN-RMS.
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Rosenberg EM, Jian X, Soubias O, Yoon HY, Yadav MP, Hammoudeh S, Pallikkuth S, Akpan I, Chen PW, Maity TK, Jenkins LM, Yohe ME, Byrd RA, Randazzo PA. The small molecule inhibitor NAV-2729 has a complex target profile including multiple ADP-ribosylation factor regulatory proteins. J Biol Chem 2023; 299:102992. [PMID: 36758799 PMCID: PMC10023970 DOI: 10.1016/j.jbc.2023.102992] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/18/2023] [Accepted: 01/20/2023] [Indexed: 02/11/2023] Open
Abstract
The ADP-ribosylation factor (Arf) GTPases and their regulatory proteins are implicated in cancer progression. NAV-2729 was previously identified as a specific inhibitor of Arf6 that reduced progression of uveal melanoma in an orthotopic xenograft. Here, our goal was to assess the inhibitory effects of NAV-2729 on the proliferation of additional cell types. We found NAV-2729 inhibited proliferation of multiple cell lines, but Arf6 expression did not correlate with NAV-2729 sensitivity, and knockdown of Arf6 affected neither cell viability nor sensitivity to NAV-2729. Furthermore, binding to native Arf6 was not detected; however, we determined that NAV-2729 inhibited both Arf exchange factors and Arf GTPase-activating proteins. ASAP1, a GTPase-activating protein linked to cancer progression, was further investigated. We demonstrated that NAV-2729 bound to the PH domain of ASAP1 and changed ASAP1 cellular distribution. However, ASAP1 knockdown did not fully recapitulate the cytoskeletal effects of NAV-2729 nor affect cell proliferation. Finally, our screens identified 48 other possible targets of NAV-2729. These results illustrate the complexities of defining targets of small molecules and identify NAV-2729 as a model PH domain-binding inhibitor.
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Gasilina A, Randazzo PA. In vitro Fluorescence Imaging-based Actin Bundling Assay. Bio Protoc 2022; 12:e4518. [PMID: 36311348 PMCID: PMC9550346 DOI: 10.21769/bioprotoc.4518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/04/2022] [Accepted: 08/18/2022] [Indexed: 12/29/2022] Open
Abstract
Understanding the molecular and structural mechanisms that govern the assembly and organization of higher-order actin architecture requires the use of in vitro actin binding and bundling assays. Crosslinking of actin filaments into bundles can be monitored in vitro via several techniques, including negative staining/electron microscopy, low-speed co-sedimentation assay/SDS-PAGE, and fluorescence staining/confocal microscopy. We and others have previously characterized the N-BAR domain of ASAP1, an ADP-ribosylation factor GTPase-activating protein, as an actin-bundling module; we further identified key lysine residues responsible for actin cross-linking. Here, we use the ASAP1 BAR domain as an example and describe a detailed procedure for observing the actin bundle formation by confocal microscopy. This protocol requires small reaction volumes and takes advantage of bright commercially available fluorescent phalloidins, making it an ideal choice for medium-throughput screening of mutants or domain truncations in their ability to bundle actin. Graphical abstract.
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Yoon HY, Maron BY, Girald-Berlingeri S, Gasilina A, Gollin JC, Jian X, Akpan I, Yohe ME, Randazzo PA, Chen PW. ERK phosphorylation is dependent on cell adhesion in a subset of pediatric sarcoma cell lines. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119264. [PMID: 35381293 DOI: 10.1016/j.bbamcr.2022.119264] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 03/15/2022] [Accepted: 03/28/2022] [Indexed: 06/14/2023]
Abstract
Osteosarcoma (OS) and Pax-Foxo1 fusion negative rhabdomyosarcoma (FN-RMS) are pediatric sarcomas with poor prognoses in patients with advanced disease. In both malignancies, an actin binding protein has been linked to poor prognosis. Integrin adhesion complexes (IACs) are closely coupled to actin networks and IAC-mediated signaling has been implicated in the progression of carcinomas. However, the relationship of IACs and actin cytoskeleton remodeling with cell signaling is understudied in pediatric sarcomas. Here, we tested the hypothesis that IAC dynamics affect ERK activation in OS and FN-RMS cell lines. Adhesion dependence of ERK activation differed among the OS and FN-RMS cells examined. In the OS cell lines, adhesion did not have a consistent effect on phospho-ERK (pERK). ERK phosphorylation in response to fetal calf serum or 1 ng/ml EGF was nearly as efficient in OS cell lines and one FN-RMS cell line in suspension as cells adherent to poly-l-lysine (PL) or fibronectin (FN). By contrast, adhesion to plastic, PL or FN increased ERK phosphorylation and was greater than additive with a 15 min exposure to 1 ng/ml EGF in three FN-RMS cell lines. Increases in pERK were partly dependent on FAK and PAK1/2 but independent of IAC maturation. As far as we are aware, this examination of adhesion-dependent signaling is the first in pediatric sarcomas and has led to the discovery of differences from the prevailing paradigms and differences in the degree of coupling between components in the signaling pathways among the cell lines.
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Gasilina A, Yoon HY, Jian X, Luo R, Randazzo PA. A lysine-rich cluster in the N-BAR domain of ARF GTPase-activating protein ASAP1 is necessary for binding and bundling actin filaments. J Biol Chem 2022; 298:101700. [PMID: 35143843 PMCID: PMC8902617 DOI: 10.1016/j.jbc.2022.101700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/25/2022] [Accepted: 01/28/2022] [Indexed: 12/05/2022] Open
Abstract
Actin filament maintenance is critical for both normal cell homeostasis and events associated with malignant transformation. The ADP-ribosylation factor GTPase-activating protein ASAP1 regulates the dynamics of filamentous actin-based structures, including stress fibers, focal adhesions, and circular dorsal ruffles. Here, we have examined the molecular basis for ASAP1 association with actin. Using a combination of structural modeling, mutagenesis, and in vitro and cell-based assays, we identify a putative-binding interface between the N-Bin-Amphiphysin-Rvs (BAR) domain of ASAP1 and actin filaments. We found that neutralization of charges and charge reversal at positions 75, 76, and 79 of ASAP1 reduced the binding of ASAP1 BAR-pleckstrin homology tandem to actin filaments and abrogated actin bundle formation in vitro. In addition, overexpression of actin-binding defective ASAP1 BAR-pleckstrin homology [K75, K76, K79] mutants prevented cellular actin remodeling in U2OS cells. Exogenous expression of [K75E, K76E, K79E] mutant of full-length ASAP1 did not rescue the reduction of cellular actin fibers consequent to knockdown of endogenous ASAP1. Taken together, our results support the hypothesis that the lysine-rich cluster in the N-BAR domain of ASAP1 is important for regulating actin filament organization.
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Wada J, Rathnayake U, Jenkins LM, Singh A, Mohammadi M, Appella E, Randazzo PA, Samelson LE. In vitro reconstitution reveals cooperative mechanisms of adapter protein-mediated activation of phospholipase C-γ1 in T cells. J Biol Chem 2022; 298:101680. [PMID: 35124007 PMCID: PMC8908268 DOI: 10.1016/j.jbc.2022.101680] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 01/31/2022] [Accepted: 02/01/2022] [Indexed: 12/16/2022] Open
Abstract
Activation of T cells upon engagement of the T cell antigen receptor rapidly leads to a number of phosphorylation and plasma membrane recruitment events. For example, translocation of phospholipase-Cγ1 (PLC−γ1) to the plasma membrane and its association with the transmembrane adapter protein LAT and two other adapter proteins, Gads and SLP-76, are critical events in the early T cell activation process. We have previously characterized the formation of a tetrameric LAT-Gads-SLP-76-PLC−γ1 complex by reconstitution in vitro and have also characterized the thermodynamics of tetramer formation. In the current study, we define how PLC−γ1 recruitment to liposomes, which serve as a plasma membrane surrogate, and PLC−γ1 activation are regulated both independently and additively by recruitment of PLC−γ1 to phosphorylated LAT, by formation of the LAT-Gads-SLP-76-PLC−γ1 tetramer, and by tyrosine phosphorylation of PLC−γ1. The recently solved structure of PLC−γ1 indicates that, in the resting state, several PLC−γ1 domains inhibit its enzymatic activity and contact with the plasma membrane. We propose the multiple cooperative steps that we observed likely lead to conformational alterations in the regulatory domains of PLC−γ1, enabling contact with its membrane substrate, disinhibition of PLC−γ1 enzymatic activity, and production of the phosphoinositide cleavage products necessary for T cell activation.
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Chen PW, Gasilina A, Yadav MP, Randazzo PA. Control of cell signaling by Arf GTPases and their regulators: Focus on links to cancer and other GTPase families. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1869:119171. [PMID: 34774605 DOI: 10.1016/j.bbamcr.2021.119171] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/23/2021] [Accepted: 11/04/2021] [Indexed: 12/31/2022]
Abstract
The ADP-ribosylation factors (Arfs) comprise a family of regulatory GTP binding proteins. The Arfs regulate membrane trafficking and cytoskeleton remodeling, processes critical for eukaryotes and which have been the focus of most studies on Arfs. A more limited literature describes a role in signaling and in integrating several signaling pathways to bring about specific cell behaviors. Here, we will highlight work describing function of Arf1, Arf6 and several effectors and regulators of Arfs in signaling.
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Sethna S, Scott PA, Giese APJ, Duncan T, Jian X, Riazuddin S, Randazzo PA, Redmond TM, Bernstein SL, Riazuddin S, Ahmed ZM. CIB2 regulates mTORC1 signaling and is essential for autophagy and visual function. Nat Commun 2021; 12:3906. [PMID: 34162842 PMCID: PMC8222345 DOI: 10.1038/s41467-021-24056-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 05/26/2021] [Indexed: 02/06/2023] Open
Abstract
Age-related macular degeneration (AMD) is a multifactorial neurodegenerative disorder. Although molecular mechanisms remain elusive, deficits in autophagy have been associated with AMD. Here we show that deficiency of calcium and integrin binding protein 2 (CIB2) in mice, leads to age-related pathologies, including sub-retinal pigment epithelium (RPE) deposits, marked accumulation of drusen markers APOE, C3, Aβ, and esterified cholesterol, and impaired visual function, which can be rescued using exogenous retinoids. Cib2 mutant mice exhibit reduced lysosomal capacity and autophagic clearance, and increased mTORC1 signaling-a negative regulator of autophagy. We observe concordant molecular deficits in dry-AMD RPE/choroid post-mortem human tissues. Mechanistically, CIB2 negatively regulates mTORC1 by preferentially binding to 'nucleotide empty' or inactive GDP-loaded Rheb. Upregulated mTORC1 signaling has been implicated in lymphangioleiomyomatosis (LAM) cancer. Over-expressing CIB2 in LAM patient-derived fibroblasts downregulates hyperactive mTORC1 signaling. Thus, our findings have significant implications for treatment of AMD and other mTORC1 hyperactivity-associated disorders.
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Kowalczyk JT, Wan X, Hernandez ER, Luo R, Lyons GC, Wilson KM, Gallardo DC, Isanogle KA, Robinson CM, Mendoza A, Heske CM, Chen JQ, Luo X, Kelly AE, Difilippantinio S, Robey RW, Thomas CJ, Sackett DL, Morrison DK, Randazzo PA, Jenkins LMM, Yohe ME. Rigosertib Induces Mitotic Arrest and Apoptosis in RAS-Mutated Rhabdomyosarcoma and Neuroblastoma. Mol Cancer Ther 2020; 20:307-319. [PMID: 33158997 DOI: 10.1158/1535-7163.mct-20-0525] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 09/16/2020] [Accepted: 10/30/2020] [Indexed: 11/16/2022]
Abstract
Relapsed pediatric rhabdomyosarcomas (RMS) and neuroblastomas (NBs) have a poor prognosis despite multimodality therapy. In addition, the current standard of care for these cancers includes vinca alkaloids that have severe toxicity profiles, further underscoring the need for novel therapies for these malignancies. Here, we show that the small-molecule rigosertib inhibits the growth of RMS and NB cell lines by arresting cells in mitosis, which leads to cell death. Our data indicate that rigosertib, like the vinca alkaloids, exerts its effects mainly by interfering with mitotic spindle assembly. Although rigosertib has the ability to inhibit oncogenic RAS signaling, we provide evidence that rigosertib does not induce cell death through inhibition of the RAS pathway in RAS-mutated RMS and NB cells. However, the combination of rigosertib and the MEK inhibitor trametinib, which has efficacy in RAS-mutated tumors, synergistically inhibits the growth of an RMS cell line, suggesting a new avenue for combination therapy. Importantly, rigosertib treatment delays tumor growth and prolongs survival in a xenograft model of RMS. In conclusion, rigosertib, through its impact on the mitotic spindle, represents a potential therapeutic for RMS.
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Soubias O, Pant S, Heinrich F, Zhang Y, Roy NS, Li J, Jian X, Yohe ME, Randazzo PA, Lösche M, Tajkhorshid E, Byrd RA. Membrane surface recognition by the ASAP1 PH domain and consequences for interactions with the small GTPase Arf1. SCIENCE ADVANCES 2020; 6:6/40/eabd1882. [PMID: 32998886 PMCID: PMC7527224 DOI: 10.1126/sciadv.abd1882] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 08/04/2020] [Indexed: 05/05/2023]
Abstract
Adenosine diphosphate-ribosylation factor (Arf) guanosine triphosphatase-activating proteins (GAPs) are enzymes that need to bind to membranes to catalyze the hydrolysis of guanosine triphosphate (GTP) bound to the small GTP-binding protein Arf. Binding of the pleckstrin homology (PH) domain of the ArfGAP With SH3 domain, ankyrin repeat and PH domain 1 (ASAP1) to membranes containing phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is key for maximum GTP hydrolysis but not fully understood. By combining nuclear magnetic resonance, neutron reflectometry, and molecular dynamics simulation, we show that binding of multiple PI(4,5)P2 molecules to the ASAP1 PH domain (i) triggers a functionally relevant allosteric conformational switch and (ii) maintains the PH domain in a well-defined orientation, allowing critical contacts with an Arf1 mimic to occur. Our model provides a framework to understand how binding of the ASAP1 PH domain to PI(4,5)P2 at the membrane may play a role in the regulation of ASAP1.
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Hebron KE, Feehan-Nelson O, Jian X, Girald SA, Randazzo PA, Yohe ME. Abstract B32: ASAP1 regulates differentiation in myoblasts and PAX-FOXO1 fusion-negative rhabdomyosarcoma. Cancer Res 2020. [DOI: 10.1158/1538-7445.pedca19-b32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Rhabdomyosarcoma (RMS), the most frequently diagnosed soft-tissue sarcoma in children, is caused by a differentiation defect in skeletal muscle precursor cells. Despite aggressive, multimodal therapies, the prognosis for recurrent PAX-FOXO1 fusion-negative RMS (FN-RMS) remains poor. Inducing differentiation in diseases defined by defective differentiation programs has led to curative therapies in cancers such as acute promyelocytic leukemia. A recent study showed that inducing differentiation slowed tumor growth and extended survival in a xenograft model of FN-RMS, identifying differentiation as a promising therapeutic target in FN-RMS. However, genes associated with differentiation are frequently found to be hijacked by tumor cells and repurposed for proinvasive programs. Therefore, better understanding of differentiation signaling and its relation to invasion could reveal novel therapeutic opportunities for patients with advanced FN-RMS. We hypothesize that ASAP1, an Arf GTPase-activating protein implicated in differentiation in normal cells and invasion in carcinoma, promotes progression by controlling proinvasive elements of differentiation signaling through focal adhesion assembly. ASAP1, an Arf GTPase-activating protein (Arf GAP), regulates integrin adhesion complexes, critical regulators of biologic processes such as proliferation, migration, and differentiation that are commonly dysregulated in cancer. ASAP1 is overexpressed in several cancers and correlates with increased metastasis and poor patient prognosis but has also been shown to promote differentiation. The mechanisms by which ASAP1 affects cancer progression and differentiation and the relationship between these effects are not yet understood. We found that ASAP1 is overexpressed in FN-RMS. ASAP1 overexpression inhibits proliferation in myoblasts, but not in FN-RMS. Knockdown of ASAP1 inhibits differentiation in both myoblast and FN-RMS cell lines, while overexpression enhances differentiation. Moreover, gene set enrichment analysis shows that myoblast differentiation-associated genes fail to become enriched upon knockdown of ASAP1. Finally, knockdown of Arf1 and Arf5, established binding partners of ASAP1, also blocks differentiation of FN-RMS cell lines, indicating that ASAP1 may regulate differentiation through its interaction with Arf GTPases. These data support our hypothesis that ASAP1 regulates the continuum of differentiation and invasion in FN-RMS. As a continuing test of the hypothesis, future studies will investigate focal adhesion assembly, dynamics, and signaling, which are processes known to be affected by ASAP1, as a mechanism for ASAP1-mediated regulation of myoblast differentiation.
Citation Format: Katie E. Hebron, Olivia Feehan-Nelson, Xiaoying Jian, Sofia A. Girald, Paul A. Randazzo, Marielle E. Yohe. ASAP1 regulates differentiation in myoblasts and PAX-FOXO1 fusion-negative rhabdomyosarcoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B32.
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Ren C, Yuan Q, Jian X, Randazzo PA, Tang W, Wu D. Small GTPase ARF6 Is a Coincidence-Detection Code for RPH3A Polarization in Neutrophil Polarization. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2020; 204:1012-1021. [PMID: 31924649 PMCID: PMC6994837 DOI: 10.4049/jimmunol.1901080] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 12/10/2019] [Indexed: 12/21/2022]
Abstract
Cell polarization is a key step for leukocytes adhesion and transmigration during leukocytes' inflammatory infiltration. Polarized localization of plasma membrane (PM) phosphatidylinositol-4-phosphate (PtdIns4P) directs the polarization of RPH3A, which contains a PtdIns4P binding site. Consequently, RPH3A mediates the RAB21 and PIP5K1C90 polarization, which is important for neutrophil adhesion to endothelia during inflammation. However, the mechanism by which RPH3A is recruited only to PM PtdIns4P rather than Golgi PtdIns4P remains unclear. By using ADP-ribosylation factor 6 (ARF6) small interfering RNA, ARF6 dominant-negative mutant ARF6(T27N), and ARF6 activation inhibitor SecinH3, we demonstrate that ARF6 plays an important role in the polarization of RPH3A, RAB21, and PIP5K1C90 in murine neutrophils. PM ARF6 is polarized and colocalized with RPH3A, RAB21, PIP5K1C90, and PM PtdIns4P in mouse and human neutrophils upon integrin stimulation. Additionally, ARF6 binds to RPH3A and enhances the interaction between the PM PtdIns4P and RPH3A. Consistent with functional roles of polarization of RPH3A, Rab21, and PIP5K1C90, ARF6 is also required for neutrophil adhesion on the inflamed endothelial layer. Our study reveals a previously unknown role of ARF6 in neutrophil polarization as being the coincidence-detection code with PM PtdIns4P. Cooperation of ARF6 and PM PtdIns4P direct RPH3A polarization, which is important for neutrophil firm adhesion to endothelia.
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Gasilina A, Vitali T, Luo R, Jian X, Randazzo PA. The ArfGAP ASAP1 Controls Actin Stress Fiber Organization via Its N-BAR Domain. iScience 2019; 22:166-180. [PMID: 31785555 PMCID: PMC6889188 DOI: 10.1016/j.isci.2019.11.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 09/30/2019] [Accepted: 11/06/2019] [Indexed: 12/11/2022] Open
Abstract
ASAP1 is a multi-domain ArfGAP that controls cell migration, spreading, and focal adhesion dynamics. Although its GAP activity contributes to remodeling of the actin cytoskeleton, it does not fully explain all cellular functions of ASAP1. Here we find that ASAP1 regulates actin filament assembly directly through its N-BAR domain and controls stress fiber maintenance. ASAP1 depletion caused defects in stress fiber organization. Conversely, overexpression of ASAP1 enhanced actin remodeling. The BAR-PH fragment was sufficient to affect actin. ASAP1 with the BAR domain replaced with the BAR domain of the related ACAP1 did not affect actin. The BAR-PH tandem of ASAP1 bound and bundled actin filaments directly, whereas the presence of the ArfGAP and the C-terminal linker/SH3 domain reduced binding and bundling of filaments by BAR-PH. Together these data provide evidence that ASAP1 may regulate the actin cytoskeleton through direct interaction of the BAR-PH domain with actin filaments.
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Roy NS, Jian X, Soubias O, Zhai P, Hall JR, Dagher JN, Coussens NP, Jenkins LM, Luo R, Akpan IO, Hall MD, Byrd RA, Yohe ME, Randazzo PA. Interaction of the N terminus of ADP-ribosylation factor with the PH domain of the GTPase-activating protein ASAP1 requires phosphatidylinositol 4,5-bisphosphate. J Biol Chem 2019; 294:17354-17370. [PMID: 31591270 DOI: 10.1074/jbc.ra119.009269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 10/02/2019] [Indexed: 12/15/2022] Open
Abstract
Arf GAP with Src homology 3 domain, ankyrin repeat, and pleckstrin homology (PH) domain 1 (ASAP1) is a multidomain GTPase-activating protein (GAP) for ADP-ribosylation factor (ARF)-type GTPases. ASAP1 affects integrin adhesions, the actin cytoskeleton, and invasion and metastasis of cancer cells. ASAP1's cellular function depends on its highly-regulated and robust ARF GAP activity, requiring both the PH and the ARF GAP domains of ASAP1, and is modulated by phosphatidylinositol 4,5-bisphosphate (PIP2). The mechanistic basis of PIP2-stimulated GAP activity is incompletely understood. Here, we investigated whether PIP2 controls binding of the N-terminal extension of ARF1 to ASAP1's PH domain and thereby regulates its GAP activity. Using [Δ17]ARF1, lacking the N terminus, we found that PIP2 has little effect on ASAP1's activity. A soluble PIP2 analog, dioctanoyl-PIP2 (diC8PIP2), stimulated GAP activity on an N terminus-containing variant, [L8K]ARF1, but only marginally affected activity on [Δ17]ARF1. A peptide comprising residues 2-17 of ARF1 ([2-17]ARF1) inhibited GAP activity, and PIP2-dependently bound to a protein containing the PH domain and a 17-amino acid-long interdomain linker immediately N-terminal to the first β-strand of the PH domain. Point mutations in either the linker or the C-terminal α-helix of the PH domain decreased [2-17]ARF1 binding and GAP activity. Mutations that reduced ARF1 N-terminal binding to the PH domain also reduced the effect of ASAP1 on cellular actin remodeling. Mutations in the ARF N terminus that reduced binding also reduced GAP activity. We conclude that PIP2 regulates binding of ASAP1's PH domain to the ARF1 N terminus, which may partially regulate GAP activity.
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Sztul E, Chen PW, Casanova JE, Cherfils J, Dacks JB, Lambright DG, Lee FJS, Randazzo PA, Santy LC, Schürmann A, Wilhelmi I, Yohe ME, Kahn RA. ARF GTPases and their GEFs and GAPs: concepts and challenges. Mol Biol Cell 2019; 30:1249-1271. [PMID: 31084567 PMCID: PMC6724607 DOI: 10.1091/mbc.e18-12-0820] [Citation(s) in RCA: 159] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 02/26/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022] Open
Abstract
Detailed structural, biochemical, cell biological, and genetic studies of any gene/protein are required to develop models of its actions in cells. Studying a protein family in the aggregate yields additional information, as one can include analyses of their coevolution, acquisition or loss of functionalities, structural pliability, and the emergence of shared or variations in molecular mechanisms. An even richer understanding of cell biology can be achieved through evaluating functionally linked protein families. In this review, we summarize current knowledge of three protein families: the ARF GTPases, the guanine nucleotide exchange factors (ARF GEFs) that activate them, and the GTPase-activating proteins (ARF GAPs) that have the ability to both propagate and terminate signaling. However, despite decades of scrutiny, our understanding of how these essential proteins function in cells remains fragmentary. We believe that the inherent complexity of ARF signaling and its regulation by GEFs and GAPs will require the concerted effort of many laboratories working together, ideally within a consortium to optimally pool information and resources. The collaborative study of these three functionally connected families (≥70 mammalian genes) will yield transformative insights into regulation of cell signaling.
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ROY NEELADRISEKHAR, Zhai P, Jian X, Jenkins L, Luo R, Yohe ME, Randazzo PA. The PH Domain of ASAP1 Binds N terminus of Arf1 in Presence of PIP2 for Efficient GTPase‐activating Protein Activity. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.477.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Li Y, Soubias O, Li J, Sun S, Randazzo PA, Byrd RA. Functional Expression and Characterization of Human Myristoylated-Arf1 in Nanodisc Membrane Mimetics. Biochemistry 2019; 58:1423-1431. [PMID: 30735034 DOI: 10.1021/acs.biochem.8b01323] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lipidated small GTP-binding proteins of the Arf family interact with multiple cellular partners and with membranes to regulate intracellular traffic and organelle structure. Here, we focus on the ADP-ribosylation factor 1 (Arf1), which interacts with numerous proteins in the Arf pathway, such as the ArfGAP ASAP1 that is highly expressed and activated in several cancer cell lines and associated with enhanced migration, invasiveness, and poor prognosis. Understanding the molecular and mechanistic details of Arf1 regulation at the membrane via structural and biophysical studies requires large quantities of fully functional protein bound to lipid bilayers. Here, we report on the production of a functional human Arf1 membrane platform on nanodiscs for biophysical studies. Large scale bacterial production of highly pure, N-myristoylated human Arf1 has been achieved, including complex isotopic labeling for nuclear magnetic resonance (NMR) studies, and the myr-Arf1 can be readily assembled in small nanoscale lipid bilayers (nanodiscs, NDs). It is determined that myr-Arf1 requires a minimum binding surface in the NDs of ∼20 lipids. Fluorescence and NMR were used to establish nucleotide exchange and ArfGAP-stimulated GTP hydrolysis at the membrane, indicating that phophoinositide stimulation of the activity of the ArfGAP ASAP1 is ≥2000-fold. Differences in nonhydrolyzable GTP analogues are observed, and GMPPCP is found to be the most stable. Combined, these observations establish a functional environment for biophysical studies of Arf1 effectors and interactions at the membrane.
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Luo R, Chen PW, Kuo JC, Jenkins L, Jian X, Waterman CM, Randazzo PA. ARAP2 inhibits Akt independently of its effects on focal adhesions. Biol Cell 2018; 110:257-270. [PMID: 30144359 DOI: 10.1111/boc.201800044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/17/2018] [Indexed: 12/15/2022]
Abstract
BACKGROUND INFORMATION ARAP2, an Arf GTPase-activating protein (Arf GAP) that binds to adaptor protein with PH domain, PTB domain and leucine zipper motifs 1 (APPL1), regulates focal adhesions (FAs). APPL1 affects FA dynamics by regulating Akt. Here, we tested the hypothesis that ARAP2 affects FAs in part by regulating Akt through APPL1. RESULTS We found that ARAP2 controlled FA dynamics dependent on its enzymatic Arf GAP activity. In some cells, ARAP2 also regulated phosphoAkt (pAkt) levels. However, ARAP2 control of FAs did not require Akt and conversely, the effects on pAkt were independent of FAs. Reducing ARAP2 expression reduced the size and number of FAs in U118, HeLa and MDA-MB-231 cells. Decreasing ARAP2 expression increased pAkt in U118 cells and HeLa cells and overexpressing ARAP2 decreased pAkt in U118 cells; in contrast, ARAP2 had no effect on pAkt in MDA-MB-231 cells. An Akt inhibitor did not block the effect of reduced ARAP2 on FAs in U118. Furthermore, the effect of ARAP2 on Akt did not require Arf GAP activity, which is necessary for effects on FAs and integrin traffic. Altering FAs by other means did not induce the same changes in pAkt as those seen by reducing ARAP2 in U118 cells. In addition, we discovered that ARAP2 and APPL1 had co-ordinated effects on pAkt in U118 cells. Reduced APPL1 expression, as for ARAP2, increased pAkt in U118 and the effect of reduced APPL1 expression was reversed by overexpressing ARAP2. Conversely, the effect of reduced ARAP2 expression was reversed by overexpressing APPL1. ARAP2 is an Arf GAP that has previously been reported to affect FAs by regulating Arf6 and integrin trafficking and to bind to the adaptor proteins APPL1. Here, we report that ARAP2 suppresses pAkt levels in cells co-ordinately with APPL1 and independently of GAP activity and its effect on the dynamic behaviour of FAs. CONCLUSIONS We conclude that ARAP2 affects Akt signalling in some cells by a mechanism independent of FAs or membrane traffic. SIGNIFICANCE Our results highlight an Arf GAP-independent function of ARAP2 in regulating Akt activity and distinguish the effect of ARAP2 on Akt from that on FAs and integrin trafficking, which requires regulation of Arf6.
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Madigan JP, Hou F, Ye L, Hu J, Dong A, Tempel W, Yohe ME, Randazzo PA, Jenkins LMM, Gottesman MM, Tong Y. The tuberous sclerosis complex subunit TBC1D7 is stabilized by Akt phosphorylation-mediated 14-3-3 binding. J Biol Chem 2018; 293:16142-16159. [PMID: 30143532 DOI: 10.1074/jbc.ra118.003525] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 08/13/2018] [Indexed: 01/19/2023] Open
Abstract
The tuberous sclerosis complex (TSC) is a negative regulator of mTOR complex 1, a signaling node promoting cellular growth in response to various nutrients and growth factors. However, several regulators in TSC signaling still await discovery and characterization. Using pulldown and MS approaches, here we identified the TSC complex member, TBC1 domain family member 7 (TBC1D7), as a binding partner for PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), a negative regulator of Akt kinase signaling. Most TBC domain-containing proteins function as Rab GTPase-activating proteins (RabGAPs), but the crystal structure of TBC1D7 revealed that it lacks residues critical for RabGAP activity. Sequence analysis identified a putative site for both Akt-mediated phosphorylation and 14-3-3 binding at Ser-124, and we found that Akt phosphorylates TBC1D7 at Ser-124. However, this phosphorylation had no effect on the binding of TBC1D7 to TSC1, but stabilized TBC1D7. Moreover, 14-3-3 protein both bound and stabilized TBC1D7 in a growth factor-dependent manner, and a phospho-deficient substitution, S124A, prevented this interaction. The crystal structure of 14-3-3ζ in complex with a phospho-Ser-124 TBC1D7 peptide confirmed the direct interaction between 14-3-3 and TBC1D7. The sequence immediately upstream of Ser-124 aligned with a canonical β-TrCP degron, and we found that the E3 ubiquitin ligase β-TrCP2 ubiquitinates TBC1D7 and decreases its stability. Our findings reveal that Akt activity determines the phosphorylation status of TBC1D7 at the phospho-switch Ser-124, which governs binding to either 14-3-3 or β-TrCP2, resulting in increased or decreased stability of TBC1D7, respectively.
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Li Y, Soubias O, Li J, Randazzo PA, Byrd RA. Interaction Between Myristoylated Human Arf1 and ASAP1 at the Membrane Surface. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Roy NS, Zhai P, Jian X, Jenkins L, Luo R, Yohe ME, Randazzo PA. Interaction of the ASAP1 PH Domain with the N Terminus of ARF1 is Controlled by Conformational Switching. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.2245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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