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Rosenberg ME, Anderson S, Farouk SS, Gibson KL, Hoover RS, Humphreys BD, Orlowski JM, Udani SM, Waitzman JS, West M, Ibrahim T. Reimagining Nephrology Fellowship Education to Meet the Future Needs of Nephrology: A Report of the American Society of Nephrology Task Force on the Future of Nephrology. Clin J Am Soc Nephrol 2023; 18:816-825. [PMID: 36848491 PMCID: PMC10278777 DOI: 10.2215/cjn.0000000000000133] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 02/16/2023] [Indexed: 03/01/2023]
Abstract
The American Society of Nephrology (ASN) Task Force on the Future of Nephrology was established in April 2022 in response to requests from the American Board of Internal Medicine and the Accreditation Council for Graduate Medical Education regarding training requirements in nephrology. Given recent changes in kidney care, ASN also charged the task force with reconsidering all aspects of the specialty's future to ensure that nephrologists are prepared to provide high-quality care for people with kidney diseases. The task force engaged multiple stakeholders to develop 10 recommendations focused on strategies needed to promote: ( 1 ) just, equitable, and high-quality care for people living with kidney diseases; ( 2 ) the value of nephrology as a specialty to nephrologists, the future nephrology workforce, the health care system, the public, and government; and ( 3 ) innovation and personalization of nephrology education across the scope of medical training. This report reviews the process, rationale, and details (the "why" and the "what") of these recommendations. In the future, ASN will summarize the "how" of implementing the final report and its 10 recommendations.
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Affiliation(s)
| | | | | | - Keisha L. Gibson
- University of North Carolina Kidney Center, Raleigh, North Carolina
| | | | | | | | - Suneel M. Udani
- Nephrology Associates of Northern Illinois and Indiana (NANI), Chicago, Illinois
| | | | | | - Tod Ibrahim
- American Society of Nephrology, Washington, DC
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2
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Vandorpe DH, Heneghan JF, Waitzman JS, McCarthy GM, Blasio A, Magraner JM, Donovan OG, Schaller LB, Shah SS, Subramanian B, Riella CV, Friedman DJ, Pollak MR, Alper SL. Apolipoprotein L1 (APOL1) cation current in HEK-293 cells and in human podocytes. Pflugers Arch 2023; 475:323-341. [PMID: 36449077 DOI: 10.1007/s00424-022-02767-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/14/2022] [Accepted: 10/25/2022] [Indexed: 12/05/2022]
Abstract
Two heterozygous missense variants (G1 and G2) of Apolipoprotein L1 (APOL1) found in individuals of recent African ancestry can attenuate the severity of infection by some forms of Trypanosoma brucei. However, these two variants within a broader African haplotype also increase the risk of kidney disease in Americans of African descent. Although overexpression of either variant G1 or G2 causes multiple pathogenic changes in cultured cells and transgenic mouse models, the mechanism(s) promoting kidney disease remain unclear. Human serum APOL1 kills trypanosomes through its cation channel activity, and cation channel activity of recombinant APOL1 has been reconstituted in lipid bilayers and proteoliposomes. Although APOL1 overexpression increases whole cell cation currents in HEK-293 cells, the ion channel activity of APOL1 has not been assessed in glomerular podocytes, the major site of APOL1-associated kidney diseases. We characterize APOL1-associated whole cell and on-cell cation currents in HEK-293 T-Rex cells and demonstrate partial inhibition of currents by anti-APOL antibodies. We detect in primary human podocytes a similar cation current inducible by interferon-γ (IFNγ) and sensitive to inhibition by anti-APOL antibody as well as by a fragment of T. brucei Serum Resistance-Associated protein (SRA). CRISPR knockout of APOL1 in human primary podocytes abrogates the IFNγ-induced, antibody-sensitive current. Our novel characterization in HEK-293 cells of heterologous APOL1-associated cation conductance inhibited by anti-APOL antibody and our documentation in primary human glomerular podocytes of endogenous IFNγ-stimulated, APOL1-mediated, SRA and anti-APOL-sensitive ion channel activity together support APOL1-mediated channel activity as a therapeutic target for treatment of APOL1-associated kidney diseases.
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Affiliation(s)
- David H Vandorpe
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - John F Heneghan
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Pathology, Brigham and Women's Hospital, Boston, MA, 02215, USA
| | - Joshua S Waitzman
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Gizelle M McCarthy
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Vertex Pharmaceuticals, Boston, MA, 02210, USA
| | - Angelo Blasio
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Vertex Pharmaceuticals, Boston, MA, 02210, USA
| | - Jose M Magraner
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,, San Diego, CA, USA
| | - Olivia G Donovan
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA
| | - Lena B Schaller
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Ludwig-Maximilians-Universitaet, 80336, Munich, Germany
| | - Shrijal S Shah
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Chroma Medicine, Cambridge, MA, 02142, USA
| | - Balajikarthick Subramanian
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Cristian V Riella
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - David J Friedman
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA
| | - Martin R Pollak
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA
| | - Seth L Alper
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA. .,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA. .,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA.
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Ko BS, Pivert KA, Rope R, Burgner AM, Waitzman JS, Halbach SM, Boyle SM, Chan L, Sozio SM. Nephrology Trainee Education Needs Assessment: Five Years and a Pandemic Later. Kidney Med 2022; 4:100548. [PMID: 36275043 PMCID: PMC9575331 DOI: 10.1016/j.xkme.2022.100548] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Affiliation(s)
| | - Kurtis A. Pivert
- American Society of Nephrology, Washington, District of Columbia
| | - Rob Rope
- Oregon Health & Science University, Portland, Oregon
| | | | | | | | | | - Lili Chan
- Icahn School of Medicine at Mount Sinai, New York, New York
| | - Stephen M. Sozio
- Johns Hopkins University School of Medicine and Bloomberg School of Public Health, Baltimore, Maryland
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Pivert KA, Boyle SM, Halbach SM, Chan L, Shah HH, Waitzman JS, Mehdi A, Norouzi S, Sozio SM. Impact of the COVID-19 Pandemic on Nephrology Fellow Training and Well-Being in the United States: A National Survey. J Am Soc Nephrol 2021; 32:1236-1248. [PMID: 33658283 PMCID: PMC8259681 DOI: 10.1681/asn.2020111636] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 01/21/2021] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The coronavirus disease 2019 (COVID-19) pandemic's effects on nephrology fellows' educational experiences, preparedness for practice, and emotional wellbeing are unknown. METHODS We recruited current adult and pediatric fellows and 2020 graduates of nephrology training programs in the United States to participate in a survey measuring COVID-19's effects on their training experiences and wellbeing. RESULTS Of 1005 nephrology fellows-in-training and recent graduates, 425 participated (response rate 42%). Telehealth was widely adopted (90% for some or all outpatient nephrology consults), as was remote learning (76% of conferences were exclusively online). Most respondents (64%) did not have in-person consults on COVID-19 inpatients; these patients were managed by telehealth visits (27%), by in-person visits with the attending faculty without fellows (29%), or by another approach (9%). A majority of fellows (84%) and graduates (82%) said their training programs successfully sustained their education during the pandemic, and most fellows (86%) and graduates (90%) perceived themselves as prepared for unsupervised practice. Although 42% indicated the pandemic had negatively affected their overall quality of life and 33% reported a poorer work-life balance, only 15% of 412 respondents who completed the Resident Well-Being Index met its distress threshold. Risk for distress was increased among respondents who perceived the pandemic had impaired their knowledge base (odds ratio [OR], 3.04; 95% confidence interval [CI], 2.00 to 4.77) or negatively affected their quality of life (OR, 3.47; 95% CI, 2.29 to 5.46) or work-life balance (OR, 3.16; 95% CI, 2.18 to 4.71). CONCLUSIONS Despite major shifts in education modalities and patient care protocols precipitated by the COVID-19 pandemic, participants perceived their education and preparation for practice to be minimally affected.
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Affiliation(s)
- Kurtis A. Pivert
- Data Science and Public Impact, American Society of Nephrology, Washington, DC
| | - Suzanne M. Boyle
- Section of Nephrology, Hypertension, and Kidney Transplantation, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania
| | - Susan M. Halbach
- Department of Pediatrics, Division of Nephrology, University of Washington and Seattle Children’s Hospital, Seattle, Washington
| | - Lili Chan
- Charles Bronfman Institute of Personalized Medicine, Department of Genetics and Genomics; Department of Medicine, Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Hitesh H. Shah
- Division of Kidney Diseases and Hypertension, Department of Medicine, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Great Neck, New York
| | - Joshua S. Waitzman
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Ali Mehdi
- Department of Nephrology and Hypertension—Glickman Urological and Kidney Institute, Cleveland Clinic Foundation, Cleveland, Ohio
| | - Sayna Norouzi
- Department of Nephrology, Loma Linda University Medical Center, Loma Linda, California
| | - Stephen M. Sozio
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine; and Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
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Affiliation(s)
- Joshua S Waitzman
- Division of Nephrology and Hypertension (J.S.W., J.L.).,Feinberg School of Medicine (J.S.W., J.T.W., J.L.), Northwestern University, Chicago, IL
| | - John T Wilkins
- Division of Cardiology (J.T.W.).,Feinberg School of Medicine (J.S.W., J.T.W., J.L.), Northwestern University, Chicago, IL
| | - Jennie Lin
- Feinberg Cardiovascular and Renal Research Institute (J.L.) .,Feinberg School of Medicine (J.S.W., J.T.W., J.L.), Northwestern University, Chicago, IL
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Bickel KG, Mann BJ, Waitzman JS, Poor TA, Rice SE, Wadsworth P. Src family kinase phosphorylation of the motor domain of the human kinesin-5, Eg5. Cytoskeleton (Hoboken) 2017. [PMID: 28646493 DOI: 10.1002/cm.21380] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Spindle formation in mammalian cells requires precise spatial and temporal regulation of the kinesin-5, Eg5, which generates outward force to establish spindle bipolarity. Our results demonstrate that Eg5 is phosphorylated in cultured cells by Src family kinases (SFKs) at three sites in the motor head: Y125, Y211, and Y231. Mutation of these sites diminishes motor activity in vitro, and replacement of endogenous Eg5 with phosphomimetic Y211 in LLC-Pk1 cells results in monopolar spindles, consistent with loss of Eg5 activity. Cells treated with SFK inhibitors show defects in spindle formation, similar to those in cells expressing the nonphosphorylatable Y211 mutant, and distinct from inhibition of other mitotic kinases. We propose that this phosphoregulatory mechanism tunes Eg5 enzymatic activity for optimal spindle morphology.
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Affiliation(s)
- Kathleen G Bickel
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611
| | - Barbara J Mann
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, 01003
| | - Joshua S Waitzman
- Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611
| | - Taylor A Poor
- Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611
| | - Sarah E Rice
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611
| | - Patricia Wadsworth
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, 01003
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Smith KP, Gifford KM, Waitzman JS, Rice SE. Survey of Phosphorylation Near Drug Binding Sites in the Protein Data Bank (PDB) and their Effects. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.1952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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8
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Rice S, Gifford KM, Waitzman JS, Poor T, Mann B, Wadsworth P. SRC Kinase Phospho-Regulation of the Human Mitotic Kinesin Eg5. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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9
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Smith KP, Gifford KM, Waitzman JS, Rice SE. Survey of phosphorylation near drug binding sites in the Protein Data Bank (PDB) and their effects. Proteins 2015; 83:25-36. [PMID: 24833420 PMCID: PMC4233198 DOI: 10.1002/prot.24605] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 04/28/2014] [Accepted: 05/09/2014] [Indexed: 12/21/2022]
Abstract
While it is currently estimated that 40 to 50% of eukaryotic proteins are phosphorylated, little is known about the frequency and local effects of phosphorylation near pharmaceutical inhibitor binding sites. In this study, we investigated how frequently phosphorylation may affect the binding of drug inhibitors to target proteins. We examined the 453 non-redundant structures of soluble mammalian drug target proteins bound to inhibitors currently available in the Protein Data Bank (PDB). We cross-referenced these structures with phosphorylation data available from the PhosphoSitePlus database. Three hundred twenty-two of 453 (71%) of drug targets have evidence of phosphorylation that has been validated by multiple methods or labs. For 132 of 453 (29%) of those, the phosphorylation site is within 12 Å of the small molecule-binding site, where it would likely alter small molecule binding affinity. We propose a framework for distinguishing between drug-phosphorylation site interactions that are likely to alter the efficacy of drugs versus those that are not. In addition we highlight examples of well-established drug targets, such as estrogen receptor alpha, for which phosphorylation may affect drug affinity and clinical efficacy. Our data suggest that phosphorylation may affect drug binding and efficacy for a significant fraction of drug target proteins.
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Affiliation(s)
- Kyle P Smith
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, 60611
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10
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Gifford KM, Waitzman JS, Poor TA, Mann B, Gonzalez MC, Wadsworth P, Rice SE. SRC Phosphorylation Regulates the Human Kinesin-5, Eg5, and Disrupts the Binding of Eg5 Inhibitors. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.4274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Waitzman JS, Rice SE. Mechanism and regulation of kinesin-5, an essential motor for the mitotic spindle. Biol Cell 2013; 106:1-12. [PMID: 24125467 DOI: 10.1111/boc.201300054] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 10/09/2013] [Indexed: 11/27/2022]
Abstract
Mitotic cell division is the most fundamental task of all living cells. Cells have intricate and tightly regulated machinery to ensure that mitosis occurs with appropriate frequency and high fidelity. A core element of this machinery is the kinesin-5 motor protein, which plays essential roles in spindle formation and maintenance. In this review, we discuss how the structural and mechanical properties of kinesin-5 motors uniquely suit them to their mitotic role. We describe some of the small molecule inhibitors and regulatory proteins that act on kinesin-5, and discuss how these regulators may influence the process of cell division. Finally, we touch on some more recently described functions of kinesin-5 motors in non-dividing cells. Throughout, we highlight a number of open questions that impede our understanding of both this motor's function and the potential utility of kinesin-5 inhibitors.
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Affiliation(s)
- Joshua S Waitzman
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, U.S.A
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12
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Vinogradova MV, Malanina GG, Waitzman JS, Rice SE, Fletterick RJ. Plant Kinesin-Like Calmodulin Binding Protein Employs Its Regulatory Domain for Dimerization. PLoS One 2013; 8:e66669. [PMID: 23805258 PMCID: PMC3689661 DOI: 10.1371/journal.pone.0066669] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [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: 11/04/2012] [Accepted: 05/13/2013] [Indexed: 11/30/2022] Open
Abstract
Kinesin-like calmodulin binding protein (KCBP), a Kinesin-14 family motor protein, is involved in the structural organization of microtubules during mitosis and trichome morphogenesis in plants. The molecular mechanism of microtubule bundling by KCBP remains unknown. KCBP binding to microtubules is regulated by Ca2+-binding proteins that recognize its C-terminal regulatory domain. In this work, we have discovered a new function of the regulatory domain. We present a crystal structure of an Arabidopsis KCBP fragment showing that the C-terminal regulatory domain forms a dimerization interface for KCBP. This dimerization site is distinct from the dimerization interface within the N-terminal domain. Side chains of hydrophobic residues of the calmodulin binding helix of the regulatory domain form the C-terminal dimerization interface. Biochemical experiments show that another segment of the regulatory domain located beyond the dimerization interface, its negatively charged coil, is unexpectedly and absolutely required to stabilize the dimers. The strong microtubule bundling properties of KCBP are unaffected by deletion of the C-terminal regulatory domain. The slow minus-end directed motility of KCBP is also unchanged in vitro. Although the C-terminal domain is not essential for microtubule bundling, we suggest that KCBP may use its two independent dimerization interfaces to support different types of bundled microtubule structures in cells. Two distinct dimerization sites may provide a mechanism for microtubule rearrangement in response to Ca2+ signaling since Ca2+- binding proteins can disengage KCBP dimers dependent on its C-terminal dimerization interface.
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Affiliation(s)
- Maia V. Vinogradova
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Galina G. Malanina
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Joshua S. Waitzman
- Department of Cell and Molecular Biology, Northwestern University, Chicago, Illinois, United States of America
| | - Sarah E. Rice
- Department of Cell and Molecular Biology, Northwestern University, Chicago, Illinois, United States of America
| | - Robert J. Fletterick
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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Waitzman JS, Larson AG, Cochran JC, Naber N, Cooke R, Jon Kull F, Pate E, Rice SE. The loop 5 element structurally and kinetically coordinates dimers of the human kinesin-5, Eg5. Biophys J 2012; 101:2760-9. [PMID: 22261065 DOI: 10.1016/j.bpj.2011.10.032] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 09/28/2011] [Accepted: 10/13/2011] [Indexed: 10/14/2022] Open
Abstract
Eg5 is a homotetrameric kinesin-5 motor protein that generates outward force on the overlapping, antiparallel microtubules (MTs) of the mitotic spindle. Upon binding an MT, an Eg5 dimer releases one ADP molecule, undergoes a slow (∼0.5 s(-1)) isomerization, and finally releases a second ADP, adopting a tightly MT-bound, nucleotide-free (APO) conformation. This conformation precedes ATP binding and stepping. Here, we use mutagenesis, steady-state and pre-steady-state kinetics, motility assays, and electron paramagnetic resonance spectroscopy to examine Eg5 monomers and dimers as they bind MTs and initiate stepping. We demonstrate that a critical element of Eg5, loop 5 (L5), accelerates ADP release during the initial MT-binding event. Furthermore, our electron paramagnetic resonance data show that L5 mediates the slow isomerization by preventing Eg5 dimer heads from binding the MT until they release ADP. Finally, we find that Eg5 having a seven-residue deletion within L5 can still hydrolyze ATP and move along MTs, suggesting that L5 is not required to accelerate subsequent steps of the motor along the MT. Taken together, these properties of L5 explain the kinetic effects of L5-directed inhibition on Eg5 activity and may direct further interventions targeting Eg5 activity.
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Affiliation(s)
- Joshua S Waitzman
- Department of Cell and Molecular Biology, Northwestern University, Chicago, Illinois, USA
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14
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Waitzman JS, Larson AG, Naber N, Landahl E, Rice SE. Intra-Motor Domain Coupling is a Strong Driver of Eg5 Motor Activity. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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15
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Bauer JH, Chang C, Morris SNS, Hozier S, Andersen S, Waitzman JS, Helfand SL. Expression of dominant-negative Dmp53 in the adult fly brain inhibits insulin signaling. Proc Natl Acad Sci U S A 2007; 104:13355-60. [PMID: 17686972 PMCID: PMC1948898 DOI: 10.1073/pnas.0706121104] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [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] [Indexed: 11/18/2022] Open
Abstract
In Drosophila melanogaster, p53 (Dmp53) is an important mediator of longevity. Expression of dominant-negative (DN) forms of Dmp53 in adult neurons, but not in muscle or fat body cells, extends lifespan. The lifespan of calorie-restricted flies is not further extended by simultaneously expressing DN-Dmp53 in the nervous system, indicating that a decrease in Dmp53 activity may be a part of the CR lifespan-extending pathway in flies. In this report, we show that selective expression of DN-Dmp53 in only the 14 insulin-producing cells (IPCs) in the brain extends lifespan to the same extent as expression in all neurons and this lifespan extension is not additive with CR. DN-Dmp53-dependent lifespan extension is accompanied by reduction of Drosophila insulin-like peptide 2 (dILP2) mRNA levels and reduced insulin signaling (IIS) in the fat body, which suggests that Dmp53 may affect lifespan by modulating insulin signaling in the fly.
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Affiliation(s)
- Johannes H. Bauer
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
| | - Chengyi Chang
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
| | - Siti Nur Sarah Morris
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
| | - Suzanne Hozier
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
| | - Sandra Andersen
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
| | - Joshua S. Waitzman
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
| | - Stephen L. Helfand
- Department of Molecular Biology, Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02903
- *To whom correspondence should be addressed. E-mail:
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