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Casey AK, Stewart NM, Zaidi N, Gray HF, Cox A, Fields HA, Orth K. FicD regulates adaptation to the unfolded protein response in the murine liver. bioRxiv 2024:2024.04.15.589620. [PMID: 38659954 PMCID: PMC11042336 DOI: 10.1101/2024.04.15.589620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The unfolded protein response (UPR) is a cellular stress response that is activated when misfolded proteins accumulate in the endoplasmic reticulum (ER). The UPR elicits a signaling cascade that results in an upregulation of protein folding machinery and cell survival signals. However, prolonged UPR responses can result in elevated cellular inflammation, damage, and even cell death. Thus, regulation of the UPR response must be tuned to the needs of the cell, sensitive enough to respond to the stress but pliable enough to be stopped after the crisis has passed. Previously, we discovered that the bi-functional enzyme FicD can modulate the UPR response via post-translational modification of BiP. FicD AMPylates BiP during homeostasis and deAMPylates BiP during stress. We found this activity is important for the physiological regulation of the exocrine pancreas. Here, we explore the role of FicD in the murine liver. Like our previous studies, livers lacking FicD exhibit enhanced UPR signaling in response to short term physiologic fasting and feeding stress. However, the livers of FicD -/- did not show marked changes in UPR signaling or damage after either chronic high fat diet (HFD) feeding or acute pathological UPR induction. Intriguingly, FicD -/- mice showed changes in UPR induction and weight loss patterns following repeated pathological UPR induction. These findings show that FicD regulates UPR responses during mild physiological stress and may play a role in maintaining resiliency of tissue through adaptation to repeated ER stress.
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Gulen B, Kinch LN, Servage KA, Blevins A, Stewart NM, Gray HF, Casey AK, Orth K. FicD Sensitizes Cellular Response to Glucose Fluctuations in Mouse Embryonic Fibroblasts. bioRxiv 2024:2024.01.22.576705. [PMID: 38328056 PMCID: PMC10849547 DOI: 10.1101/2024.01.22.576705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
During homeostasis, the endoplasmic reticulum (ER) maintains productive transmembrane and secretory protein folding that is vital for proper cellular function. The ER-resident HSP70 chaperone, BiP, plays a pivotal role in sensing ER stress to activate the unfolded protein response (UPR). BiP function is regulated by the bifunctional enzyme FicD that mediates AMPylation and deAMPylation of BiP in response to changes in ER stress. AMPylated BiP acts as a molecular rheostat to regulate UPR signaling, yet little is known about the molecular consequences of FicD loss. In this study, we investigate the role of FicD in mouse embryonic fibroblast (MEF) response to pharmacologically and metabolically induced ER stress. We find differential BiP AMPylation signatures when comparing robust chemical ER stress inducers to physiological glucose starvation stress and recovery. Wildtype MEFs respond to pharmacological ER stress by downregulating BiP AMPylation. Conversely, BiP AMPylation in wildtype MEFs increases upon metabolic stress induced by glucose starvation. Deletion of FicD results in widespread gene expression changes under baseline growth conditions. In addition, FicD null MEFs exhibit dampened UPR signaling, altered cell stress recovery response, and unconstrained protein secretion. Taken together, our findings indicate that FicD is important for tampering UPR signaling, stress recovery, and the maintenance of secretory protein homeostasis. Significance Statement The chaperone BiP plays a key quality control role in the endoplasmic reticulum, the cellular location for the production, folding, and transport of secreted proteins. The enzyme FicD regulates BiP's activity through AMPylation and deAMPylation. Our study unveils the importance of FicD in regulating BiP and the unfolded protein response (UPR) during stress. We identify distinct BiP AMPylation signatures for different stressors, highlighting FicD's nuanced control. Deletion of FicD causes widespread gene expression changes, disrupts UPR signaling, alters stress recovery, and perturbs protein secretion in cells. These observations underscore the pivotal contribution of FicD for preserving secretory protein homeostasis. Our findings deepen the understanding of FicD's role in maintaining cellular resilience and open avenues for therapeutic strategies targeting UPR-associated diseases.
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Casey AK, Gray HF, Chimalapati S, Hernandez G, Moehlman AT, Stewart N, Fields HA, Gulen B, Servage KA, Stefanius K, Blevins A, Evers BM, Krämer H, Orth K. Fic-mediated AMPylation tempers the unfolded protein response during physiological stress. Proc Natl Acad Sci U S A 2022; 119:e2208317119. [PMID: 35914137 PMCID: PMC9371680 DOI: 10.1073/pnas.2208317119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 07/09/2022] [Indexed: 12/14/2022] Open
Abstract
The proper balance of synthesis, folding, modification, and degradation of proteins, also known as protein homeostasis, is vital to cellular health and function. The unfolded protein response (UPR) is activated when the mechanisms maintaining protein homeostasis in the endoplasmic reticulum become overwhelmed. However, prolonged or strong UPR responses can result in elevated inflammation and cellular damage. Previously, we discovered that the enzyme filamentation induced by cyclic-AMP (Fic) can modulate the UPR response via posttranslational modification of binding immunoglobulin protein (BiP) by AMPylation during homeostasis and deAMPylation during stress. Loss of fic in Drosophila leads to vision defects and altered UPR activation in the fly eye. To investigate the importance of Fic-mediated AMPylation in a mammalian system, we generated a conditional null allele of Fic in mice and characterized the effect of Fic loss on the exocrine pancreas. Compared to controls, Fic-/- mice exhibit elevated serum markers for pancreatic dysfunction and display enhanced UPR signaling in the exocrine pancreas in response to physiological and pharmacological stress. In addition, both fic-/- flies and Fic-/- mice show reduced capacity to recover from damage by stress that triggers the UPR. These findings show that Fic-mediated AMPylation acts as a molecular rheostat that is required to temper the UPR response in the mammalian pancreas during physiological stress. Based on these findings, we propose that repeated physiological stress in differentiated tissues requires this rheostat for tissue resilience and continued function over the lifetime of an animal.
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Affiliation(s)
- Amanda K. Casey
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Hillery F. Gray
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Suneeta Chimalapati
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Genaro Hernandez
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Andrew T. Moehlman
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Nathan Stewart
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Hazel A. Fields
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Burak Gulen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Kelly A. Servage
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Karoliina Stefanius
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Aubrie Blevins
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Bret M. Evers
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Helmut Krämer
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
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De Nisco NJ, Casey AK, Kanchwala M, Lafrance AE, Coskun FS, Kinch LN, Grishin NV, Xing C, Orth K. Manipulation of IRE1-Dependent MAPK Signaling by a Vibrio Agonist-Antagonist Effector Pair. mSystems 2021; 6:e00872-20. [PMID: 33563785 PMCID: PMC7883537 DOI: 10.1128/msystems.00872-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 01/19/2021] [Indexed: 12/05/2022] Open
Abstract
Diverse bacterial pathogens employ effector delivery systems to disrupt vital cellular processes in the host (N. M. Alto and K. Orth, Cold Spring Harbor Perspect Biol 4:a006114, 2012, https://doi.org/10.1101/cshperspect.a006114). The type III secretion system 1 of the marine pathogen Vibrio parahaemolyticus utilizes the sequential action of four effectors to induce a rapid, proinflammatory cell death uniquely characterized by a prosurvival host transcriptional response (D. L. Burdette, M. L. Yarbrough, A Orvedahl, C. J. Gilpin, and K. Orth, Proc Natl Acad Sci USA 105:12497-12502, 2008, https://doi.org/10.1073/pnas.0802773105; N. J. De Nisco, M. Kanchwala, P. Li, J. Fernandez, C. Xing, and K. Orth, Sci Signal 10:eaa14501, 2017, https://doi.org/10.1126/scisignal.aal4501). Herein, we show that this prosurvival response is caused by the action of the channel-forming effector VopQ that targets the host V-ATPase, resulting in lysosomal deacidification and inhibition of lysosome-autophagosome fusion. Recent structural studies have shown how VopQ interacts with the V-ATPase and, while in the ER, a V-ATPase assembly intermediate can interact with VopQ, causing a disruption in membrane integrity. Additionally, we observed that VopQ-mediated disruption of the V-ATPase activates the IRE1 branch of the unfolded protein response (UPR), resulting in an IRE1-dependent activation of ERK1/2 MAPK signaling. We also find that this early VopQ-dependent induction of ERK1/2 phosphorylation is terminated by the VopS-mediated inhibitory AMPylation of Rho GTPase signaling. Since VopS dampens VopQ-induced IRE1-dependent ERK1/2 activation, we propose that IRE1 activates ERK1/2 phosphorylation at or above the level of Rho GTPases. This study illustrates how temporally induced effectors can work as in tandem as agonist/antagonist to manipulate host signaling and reveals new connections between V-ATPase function, UPR, and MAPK signaling.IMPORTANCE Vibrio parahaemolyticus is a seafood-borne pathogen that encodes two type 3 secretion systems (T3SS). The first system, T3SS1, is thought to be maintained in all strains of V. parahaemolyticus to maintain survival in the environment, whereas the second system, T3SS2, is linked to clinical isolates and disease in humans. Here, we found that first system targets evolutionarily conserved signaling systems to manipulate host cells, eventually causing a rapid, orchestrated cells death within 3 h. We have found that the T3SS1 injects virulence factors that temporally manipulate host signaling. Within the first hour of infection, the effector VopQ acts first by activating host survival signals while diminishing the host cell apoptotic machinery. Less than an hour later, another effector, VopS, reverses activation and inhibition of these signaling systems, ultimately leading to death of the host cell. This work provides example of how pathogens have evolved to manipulate the interplay between T3SS effectors to regulate host signaling pathways.
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Affiliation(s)
- Nicole J De Nisco
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Amanda K Casey
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Mohammed Kanchwala
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Alexander E Lafrance
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Fatma S Coskun
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Lisa N Kinch
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Nick V Grishin
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Chao Xing
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Population and Data Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Peng W, Casey AK, Fernandez J, Carpinone EM, Servage KA, Chen Z, Li Y, Tomchick DR, Starai VJ, Orth K. A distinct inhibitory mechanism of the V-ATPase by Vibrio VopQ revealed by cryo-EM. Nat Struct Mol Biol 2020; 27:589-597. [PMID: 32424347 DOI: 10.1038/s41594-020-0429-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 04/01/2020] [Indexed: 12/18/2022]
Abstract
The Vibrio parahaemolyticus T3SS effector VopQ targets host-cell V-ATPase, resulting in blockage of autophagic flux and neutralization of acidic compartments. Here, we report the cryo-EM structure of VopQ bound to the Vo subcomplex of the V-ATPase. VopQ inserts into membranes and forms an unconventional pore while binding directly to subunit c of the V-ATPase membrane-embedded subcomplex Vo. We show that VopQ arrests yeast growth in vivo by targeting the immature Vo subcomplex in the endoplasmic reticulum (ER), thus providing insight into the observation that VopQ kills cells in the absence of a functional V-ATPase. VopQ is a bacterial effector that has been discovered to inhibit a host-membrane megadalton complex by coincidentally binding its target, inserting into a membrane and disrupting membrane potential. Collectively, our results reveal a mechanism by which bacterial effectors modulate host cell biology and provide an invaluable tool for future studies on V-ATPase-mediated membrane fusion and autophagy.
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Affiliation(s)
- Wei Peng
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Amanda K Casey
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jessie Fernandez
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | | | - Kelly A Servage
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Zhe Chen
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yang Li
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Diana R Tomchick
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Vincent J Starai
- Department of Microbiology, University of Georgia, Athens, GA, USA
- Department of Infectious Diseases, University of Georgia, Athens, GA, USA
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Moehlman AT, Casey AK, Servage K, Orth K, Krämer H. Adaptation to constant light requires Fic-mediated AMPylation of BiP to protect against reversible photoreceptor degeneration. eLife 2018; 7:e38752. [PMID: 30015618 PMCID: PMC6066327 DOI: 10.7554/elife.38752] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 07/16/2018] [Indexed: 12/13/2022] Open
Abstract
In response to environmental, developmental, and pathological stressors, cells engage homeostatic pathways to maintain their function. Among these pathways, the Unfolded Protein Response protects cells from the accumulation of misfolded proteins in the ER. Depending on ER stress levels, the ER-resident Fic protein catalyzes AMPylation or de-AMPylation of BiP, the major ER chaperone and regulator of the Unfolded Protein Response. This work elucidates the importance of the reversible AMPylation of BiP in maintaining the Drosophila visual system in response to stress. After 72 hr of constant light, photoreceptors of fic-null and AMPylation-resistant BiPT366A mutants, but not wild-type flies, display loss of synaptic function, disintegration of rhabdomeres, and excessive activation of ER stress reporters. Strikingly, this phenotype is reversible: photoreceptors regain their structure and function within 72 hr once returned to a standard light:dark cycle. These findings show that Fic-mediated AMPylation of BiP is required for neurons to adapt to transient stress demands.
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Affiliation(s)
- Andrew T Moehlman
- Department of NeuroscienceUT Southwestern Medical CenterDallasUnited States
| | - Amanda K Casey
- Department of Molecular BiologyUT Southwestern Medical CenterDallasUnited States
| | - Kelly Servage
- Department of Molecular BiologyUT Southwestern Medical CenterDallasUnited States
- Department of BiochemistryUT Southwestern Medical CenterDallasUnited States
- Howard Hughes Medical InstituteDallasUnited States
| | - Kim Orth
- Department of Molecular BiologyUT Southwestern Medical CenterDallasUnited States
- Department of BiochemistryUT Southwestern Medical CenterDallasUnited States
- Howard Hughes Medical InstituteDallasUnited States
| | - Helmut Krämer
- Department of NeuroscienceUT Southwestern Medical CenterDallasUnited States
- Department of Cell BiologyUT Southwestern Medical CenterDallasUnited States
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Casey AK, Moehlman AT, Zhang JK, Servage KA, Krämer HK, Orth K. Fic‐mediated deAMPylation is not dependent on homo‐dimerization and rescues toxic AMPylation in flies. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.542.25] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Amanda K. Casey
- Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTX
| | | | - Junmei K. Zhang
- Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTX
- Howard Hughes Medical InstituteDallasTX
| | - Kelly A. Servage
- Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTX
- Howard Hughes Medical InstituteDallasTX
| | - Helmut K. Krämer
- NeuroscienceUniversity of Texas Southwestern Medical CenterDallasTX
| | - Kim Orth
- Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTX
- BiochemistryUniversity of Texas Southwestern Medical CenterDallasTX
- Howard Hughes Medical InstituteDallasTX
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Abstract
Posttranslational modifications are covalent changes made to proteins that typically alter the function or location of the protein. AMPylation is an emerging posttranslational modification that involves the addition of adenosine monophosphate (AMP) to a protein. Like other, more well-studied posttranslational modifications, AMPylation is predicted to regulate the activity of the modified target proteins. However, the scope of this modification both in bacteria and in eukaryotes remains to be fully determined. In this review, we provide an up to date overview of the known AMPylating enzymes, the regulation of these enzymes, and the effect of this modification on target proteins.
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Affiliation(s)
- Amanda K. Casey
- Department of Molecular Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard NA5.120F, Dallas, Texas 75390-9148, United States
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard NA5.120F, Dallas, Texas 75390-9148, United States
- Howard Hughes Medical Institute, 6000 Harry Hines Boulevard NA5.120F, Dallas, Texas 75390-9148, United States
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Casey AK, Moehlman AT, Zhang J, Servage KA, Krämer H, Orth K. Fic-mediated deAMPylation is not dependent on homodimerization and rescues toxic AMPylation in flies. J Biol Chem 2018; 293:1550. [PMID: 29414767 DOI: 10.1074/jbc.aac118.001798] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Casey AK, Moehlman AT, Zhang J, Servage KA, Krämer H, Orth K. Fic-mediated deAMPylation is not dependent on homodimerization and rescues toxic AMPylation in flies. J Biol Chem 2017; 292:21193-21204. [PMID: 29089387 DOI: 10.1074/jbc.m117.799296] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 10/17/2017] [Indexed: 01/30/2023] Open
Abstract
Protein chaperones play a critical role in proteostasis. The activity of the major endoplasmic reticulum chaperone BiP (GRP78) is regulated by Fic-mediated AMPylation during resting states. By contrast, during times of stress, BiP is deAMPylated. Here, we show that excessive AMPylation by a constitutively active FicE247G mutant is lethal in Drosophila This lethality is cell-autonomous, as directed expression of the mutant FicE247G to the fly eye does not kill the fly but rather results in a rough and reduced eye. Lethality and eye phenotypes are rescued by the deAMPylation activity of wild-type Fic. Consistent with Fic acting as a deAMPylation enzyme, its activity was both time- and concentration-dependent. Furthermore, Fic deAMPylation activity was sufficient to suppress the AMPylation activity mediated by the constitutively active FicE247G mutant in Drosophila S2 lysates. Further, we show that the dual enzymatic activity of Fic is, in part, regulated by Fic dimerization, as loss of this dimerization increases AMPylation and reduces deAMPylation of BiP.
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Affiliation(s)
| | | | - Junmei Zhang
- From the Department of Molecular Biology.,the Howard Hughes Medical Institute, and
| | - Kelly A Servage
- From the Department of Molecular Biology.,the Howard Hughes Medical Institute, and
| | | | - Kim Orth
- From the Department of Molecular Biology, .,the Howard Hughes Medical Institute, and.,the Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9148
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Casey AK, Chen S, Novick P, Ferro-Novick S, Wente SR. Nuclear pore complex integrity requires Lnp1, a regulator of cortical endoplasmic reticulum. Mol Biol Cell 2015; 26:2833-44. [PMID: 26041935 PMCID: PMC4571342 DOI: 10.1091/mbc.e15-01-0053] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 04/21/2015] [Accepted: 05/27/2015] [Indexed: 12/31/2022] Open
Abstract
The nuclear envelope (NE) and endoplasmic reticulum (ER) are components of the same contiguous membrane system and yet have distinct cellular functions. Mounting evidence suggests roles for some ER proteins in the NE for proper nuclear pore complex (NPC) structure and function. In this study, we identify a NE role in Saccharomyces cerevisiae for Lnp1 and Sey1, proteins required for proper cortical ER formation. Both lnp1Δ and sey1Δ mutants exhibit synthetic genetic interactions with mutants in genes encoding key NPC structural components. Both Lnp1 and Sey1 physically associate with other ER components that have established NPC roles, including Rtn1, Yop1, Pom33, and Per33. Of interest, lnp1Δ rtn1Δ mutants but not rtn1Δ sey1Δ mutants exhibit defects in NPC distribution. Furthermore, the essential NPC assembly factor Ndc1 has altered interactions in the absence of Sey1. Lnp1 dimerizes in vitro via its C-terminal zinc finger motif, a property that is required for proper ER structure but not NPC integrity. These findings suggest that Lnp1's role in NPC integrity is separable from functions in the ER and is linked to Ndc1 and Rtn1 interactions.
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Affiliation(s)
- Amanda K Casey
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Shuliang Chen
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093 Howard Hughes Medical Institute, University of California at San Diego, La Jolla, CA 92093
| | - Susan Ferro-Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093
| | - Susan R Wente
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 )
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12
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Abstract
In fungi, nuclear pore complexes are free to move through the nuclear envelope; however, little is known about how movement is regulated. New evidence reveals roles for molecular motors and potential impacts on genomic organization.
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Affiliation(s)
- Amanda K Casey
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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