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Safavian D, Kim MS, Xie H, El-Zeiry M, Palander O, Dai L, Collins RF, Froese C, Shannon R, Nagata KI, Trimble WS. Septin-mediated RhoA activation engages the exocyst complex to recruit the cilium transition zone. J Cell Biol 2023; 222:e201911062. [PMID: 36912772 PMCID: PMC10039714 DOI: 10.1083/jcb.201911062] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 11/14/2019] [Revised: 01/25/2022] [Accepted: 01/05/2023] [Indexed: 03/14/2023] Open
Abstract
Septins are filamentous GTPases that play important but poorly characterized roles in ciliogenesis. Here, we show that SEPTIN9 regulates RhoA signaling at the base of cilia by binding and activating the RhoA guanine nucleotide exchange factor, ARHGEF18. GTP-RhoA is known to activate the membrane targeting exocyst complex, and suppression of SEPTIN9 causes disruption of ciliogenesis and mislocalization of an exocyst subunit, SEC8. Using basal body-targeted proteins, we show that upregulating RhoA signaling at the cilium can rescue ciliary defects and mislocalization of SEC8 caused by global SEPTIN9 depletion. Moreover, we demonstrate that the transition zone components, RPGRIP1L and TCTN2, fail to accumulate at the transition zone in cells lacking SEPTIN9 or depleted of the exocyst complex. Thus, SEPTIN9 regulates the recruitment of transition zone proteins on Golgi-derived vesicles by activating the exocyst via RhoA to allow the formation of primary cilia.
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Affiliation(s)
- Darya Safavian
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Moshe S. Kim
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Hong Xie
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Maha El-Zeiry
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Oliva Palander
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Lu Dai
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Richard F. Collins
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Carol Froese
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Rachel Shannon
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Koh-ichi Nagata
- Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan
| | - William S. Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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2
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Ahmad Z, Liaqat R, Palander O, Bilal M, Zeb S, Ahmad F, Jawad Khan M, Umair M. Genetic overview of postaxial polydactyly: Updated classification. Clin Genet 2023; 103:3-15. [PMID: 36071556 DOI: 10.1111/cge.14224] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [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: 07/21/2022] [Revised: 08/26/2022] [Accepted: 09/01/2022] [Indexed: 12/13/2022]
Abstract
Polydactyly or polydactylism, also known as a hyperdactyly, is a congenital limb defect with various morphologic phenotypes. Apart from physical and functional impairments, the presence of polydactyly is an indication of an underlying syndrome in the newborn. Usually, it follows as an autosomal dominant/recessive inheritance pattern with defects in the limb development's anteroposterior patterning. Although mutations in several genes have been associated with polydactyly; however, the exact underlying cause, pathways, and disease mechanisms are still unexplored, thus making it of multi-factorial origin. Polydactyly is divided into three subtypes; radial, ulnar, and central polydactyly. So far, 11 loci (PAPA1-PAPA11) and seven human genes have been reported to cause non-syndromic postaxial polydactyly in humans, including the ZNF141, GLI3, IQCE, GLI1, FAM92A1, KIAA0825, and DACH1. In this review, we discuss emerging evidences of clinical and molecular characterization of polydactyly types in term of the involvement of newly associated genes and loci for non-syndromic postaxial polydactyly, and how these might impact our understanding of the genetic mechanisms and molecular etiology involved in the cause of polydactyly.
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Affiliation(s)
- Zaheer Ahmad
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Romana Liaqat
- Institute of Chemical Sciences, Gomal University, Dera Ismail Khan, Pakistan
| | - Oliva Palander
- Faculty of Medicine, Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.,Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Muhammad Bilal
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
| | - Shah Zeb
- Institute for Advanced Study, Shenzhen University, Shenzhen, People's Republic of China.,College of Physics and Optoelectronics Engineering, Shenzhen University, Shenzhen, People's Republic of China
| | - Farooq Ahmad
- Department of Biochemistry, Women University Swabi, Swabi, Pakistan
| | - Muhammad Jawad Khan
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Muhammad Umair
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia.,Department of Life Sciences, School of Science, University of Management and Technology (UMT), Lahore, Pakistan
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Soroor F, Kim MS, Palander O, Balachandran Y, Collins RF, Benlekbir S, Rubinstein JL, Trimble WS. Revised subunit order of mammalian septin complexes explains their in vitro polymerization properties. Mol Biol Cell 2020; 32:289-300. [PMID: 33263440 PMCID: PMC8098831 DOI: 10.1091/mbc.e20-06-0398] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Septins are conserved GTP-binding cytoskeletal proteins that polymerize into filaments by end-to-end joining of hetero-oligomeric complexes. In human cells, both hexamers and octamers exist, and crystallography studies predicted the order of the hexamers to be SEPT7-SEPT6-SEPT2-SEPT2-SEPT6-SEPT7, while octamers are thought to have the same core, but with SEPT9 at the ends. However, based on this septin organization, octamers and hexamers would not be expected to copolymerize due to incompatible ends. Here we isolated hexamers and octamers of specific composition from human cells and show that hexamers and octamers polymerize individually and, surprisingly, with each other. Binding of the Borg homology domain 3 (BD3) domain of Borg3 results in distinctive clustering of each filament type. Moreover, we show that the organization of hexameric and octameric complexes is inverted compared with its original prediction. This revised septin organization is congruent with the organization and behavior of yeast septins suggesting that their properties are more conserved than was previously thought.
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Affiliation(s)
- Forooz Soroor
- Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON M5G 1A8, Canada
| | - Moshe S Kim
- Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Oliva Palander
- Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON M5G 1A8, Canada
| | - Yadu Balachandran
- Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Richard F Collins
- Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Samir Benlekbir
- Molecular Medicine Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - John L Rubinstein
- Molecular Medicine Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON M5G 1A8, Canada
| | - William S Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON M5G 1A8, Canada
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Palander O, Trimble WS. DIAPH1 regulates ciliogenesis and trafficking in primary cilia. FASEB J 2020; 34:16516-16535. [PMID: 33124112 DOI: 10.1096/fj.202001178r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [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: 05/11/2020] [Revised: 09/08/2020] [Accepted: 10/12/2020] [Indexed: 01/29/2023]
Abstract
Primary cilia are critical hubs for several signaling pathways, and defects in ciliogenesis or cilia maintenance produce a range of diseases collectively known as ciliopathies. Ciliogenesis requires vesicle trafficking along a network of microtubules and actin filaments to the basal body. The DIAPH1 (Diaphanous-related formin) family of formins promotes both actin polymerization and EB1-dependent microtubule (MT) stability. EB1 and EB3 have previously been implicated in cilia biogenesis to carry out centrosome-related functions. However, the role of DIAPH1 proteins had not been examined. Here we show that the depletion of DIAPH1 decreased ciliogenesis, cilia length, and reduced trafficking within cilia. Additionally, both actin nucleating and microtubule-stabilizing properties of DIAPH1 are important for their cilia functions. To assess their roles in ciliogenesis in isolation, we targeted DIAPH1 specifically to the basal body, which caused an increase in cilia length and increased trafficking within cilia. Intriguingly, expression of DIAPH1 mutants associated with human deafness and microcephaly impaired ciliation and caused cilia elongation and bulb formation. These results suggest that the actin and microtubule functions of DIAPH1 proteins regulate cilia maintenance in part by regulating vesicular trafficking to the base of the primary cilia.
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Affiliation(s)
- Oliva Palander
- Cell Biology Program, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - William S Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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Abstract
Septins are a family of GTP-binding proteins that associate with cellular membranes and the cytoskeleton. Their ability to polymerize into filamentous structures permits them to serve as diffusion barriers for membrane proteins and as multi-molecular scaffolds that recruit components of signaling pathways. At the cellular level, septins contribute to the regulation of numerous processes, including cytokinesis, cell polarity, cell migration, and many others. In this review, we discuss emerging evidence for roles of mammalian septins in the biogenesis and function of flagella and cilia, and how this may impact human diseases such as ciliopathies.
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Affiliation(s)
- Oliva Palander
- Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada.,Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - Maha El-Zeiry
- Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada.,Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - William S Trimble
- Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada.,Department of Biochemistry, University of TorontoToronto, ON, Canada.,Department of Physiology, University of TorontoToronto, ON, Canada
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Carnevale J, Palander O, Seifried LA, Dick FA. DNA damage signals through differentially modified E2F1 molecules to induce apoptosis. Mol Cell Biol 2012; 32:900-12. [PMID: 22184068 PMCID: PMC3295199 DOI: 10.1128/mcb.06286-11] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [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: 09/14/2011] [Accepted: 12/12/2011] [Indexed: 01/28/2023] Open
Abstract
E2F transcription can lead to cell proliferation or apoptosis, indicating that E2Fs control opposing functions. In a similar manner, DNA double-strand breaks can signal to induce cell cycle arrest or apoptosis. Specifically, pRB is activated following DNA damage, allowing it to bind to E2Fs and block transcription at cell cycle promoters; however, E2F1 is simultaneously activated, leading to transcription at proapoptotic promoters. We examined this paradoxical control of E2F transcription by studying how E2F1's interaction with pRB is regulated following DNA damage. Our work reveals that DNA damage signals create multiple forms of E2F1 that contain mutually exclusive posttranslational modifications. Specifically, E2F1 phospho-serine 364 is found only in complex with pRB, while E2F1 phosphorylation at serine 31 and acetylation function to create a pRB-free form of E2F1. Both pRB-bound and pRB-free modifications on E2F1 are essential for the activation of TA-p73 and the maximal induction of apoptosis. Chromatin immunoprecipitation demonstrated that E2F1 phosphorylated on serine 364 is also present at proapoptotic gene promoters during the induction of apoptosis. This indicates that distinct populations of E2F1 are organized in response to DNA damage signaling. Surprisingly, these complexes act in parallel to activate transcription of proapoptotic genes. Our data suggest that DNA damage signals alter pRB and E2F1 to engage them in functions leading to apoptotic induction that are distinct from pRB-E2F regulation in cell cycle control.
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Affiliation(s)
- Jasmyne Carnevale
- London Regional Cancer Program
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Oliva Palander
- London Regional Cancer Program
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Laurie A. Seifried
- London Regional Cancer Program
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Frederick A. Dick
- London Regional Cancer Program
- Children's Health Research Institute
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
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Julian LM, Palander O, Seifried LA, Foster JEG, Dick FA. Characterization of an E2F1-specific binding domain in pRB and its implications for apoptotic regulation. Oncogene 2007; 27:1572-9. [PMID: 17891180 DOI: 10.1038/sj.onc.1210803] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The retinoblastoma protein (pRB) has the dual capability to negatively regulate both E2F-induced cell cycle entry and E2F1-induced apoptosis. In this report, we characterize a unique pRB-E2F1 interaction. Using mutagenesis to disrupt E2F1 binding, we find that the ability of pRB to regulate E2F1-induced apoptosis is diminished when this interaction is lost. Strikingly, this mutant form of pRB retains the ability to control E2F responsive cell cycle genes and blocks cell proliferation. These functional properties are the reciprocal of a previously described E2F binding mutant of pRB that interacts with E2F1, but lacks the ability to interact with other E2Fs. Our work shows that these distinct interactions allow pRB to separately regulate E2F-induced cell proliferation and apoptosis. This suggests a novel form of regulation whereby separate types of binding contacts between the same types of molecules can confer distinct functional outcomes.
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Affiliation(s)
- L M Julian
- London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada
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