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Pei J, Cong Q. Computational analysis of regulatory regions in human protein kinases. Protein Sci 2023; 32:e4764. [PMID: 37632170 PMCID: PMC10503413 DOI: 10.1002/pro.4764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/08/2023] [Accepted: 08/22/2023] [Indexed: 08/27/2023]
Abstract
Eukaryotic proteins often feature modular domain structures comprising globular domains that are connected by linker regions and intrinsically disordered regions that may contain important functional motifs. The intramolecular interactions of globular domains and nonglobular regions can play critical roles in different aspects of protein function. However, studying these interactions and their regulatory roles can be challenging due to the flexibility of nonglobular regions, the long insertions separating interacting modules, and the transient nature of some interactions. Obtaining the experimental structures of multiple domains and functional regions is more difficult than determining the structures of individual globular domains. High-quality structural models generated by AlphaFold offer a unique opportunity to study intramolecular interactions in eukaryotic proteins. In this study, we systematically explored intramolecular interactions between human protein kinase domains (KDs) and potential regulatory regions, including globular domains, N- and C-terminal tails, long insertions, and distal nonglobular regions. Our analysis identified intramolecular interactions between human KDs and 35 different types of globular domains, exhibiting a variety of interaction modes that could contribute to orthosteric or allosteric regulation of kinase activity. We also identified prevalent interactions between human KDs and their flanking regions (N- and C-terminal tails). These interactions exhibit group-specific characteristics and can vary within each specific kinase group. Although long-range interactions between KDs and nonglobular regions are relatively rare, structural details of these interactions offer new insights into the regulation mechanisms of several kinases, such as HASPIN, MAPK7, MAPK15, and SIK1B.
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Affiliation(s)
- Jimin Pei
- Eugene McDermott Center for Human Growth and DevelopmentUniversity of Texas Southwestern Medical CenterDallasTexasUSA
- Department of BiophysicsUniversity of Texas Southwestern Medical CenterDallasTexasUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTexasUSA
| | - Qian Cong
- Eugene McDermott Center for Human Growth and DevelopmentUniversity of Texas Southwestern Medical CenterDallasTexasUSA
- Department of BiophysicsUniversity of Texas Southwestern Medical CenterDallasTexasUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTexasUSA
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2
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Hogg EKJ, Findlay GM. Functions of SRPK, CLK and DYRK kinases in stem cells, development, and human developmental disorders. FEBS Lett 2023; 597:2375-2415. [PMID: 37607329 PMCID: PMC10952393 DOI: 10.1002/1873-3468.14723] [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: 06/05/2023] [Revised: 07/08/2023] [Accepted: 07/18/2023] [Indexed: 08/24/2023]
Abstract
Human developmental disorders encompass a wide range of debilitating physical conditions and intellectual disabilities. Perturbation of protein kinase signalling underlies the development of some of these disorders. For example, disrupted SRPK signalling is associated with intellectual disabilities, and the gene dosage of DYRKs can dictate the pathology of disorders including Down's syndrome. Here, we review the emerging roles of the CMGC kinase families SRPK, CLK, DYRK, and sub-family HIPK during embryonic development and in developmental disorders. In particular, SRPK, CLK, and DYRK kinase families have key roles in developmental signalling and stem cell regulation, and can co-ordinate neuronal development and function. Genetic studies in model organisms reveal critical phenotypes including embryonic lethality, sterility, musculoskeletal errors, and most notably, altered neurological behaviours arising from defects of the neuroectoderm and altered neuronal signalling. Further unpicking the mechanisms of specific kinases using human stem cell models of neuronal differentiation and function will improve our understanding of human developmental disorders and may provide avenues for therapeutic strategies.
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Affiliation(s)
- Elizabeth K. J. Hogg
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life SciencesUniversity of DundeeUK
| | - Greg M. Findlay
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life SciencesUniversity of DundeeUK
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3
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Rodriguez Gallo MC, Uhrig RG. Phosphorylation mediated regulation of RNA splicing in plants. FRONTIERS IN PLANT SCIENCE 2023; 14:1249057. [PMID: 37780493 PMCID: PMC10539000 DOI: 10.3389/fpls.2023.1249057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 08/22/2023] [Indexed: 10/03/2023]
Abstract
For the past two decades, the study of alternative splicing (AS) and its involvement in plant development and stress response has grown in popularity. Only recently however, has the focus shifted to the study of how AS regulation (or lack-thereof) affects downstream mRNA and protein landscapes and how these AS regulatory events impact plant development and stress tolerance. In humans, protein phosphorylation represents one of the predominant mechanisms by which AS is regulated and thus the protein kinases governing these phosphorylation events are of interest for further study. Large-scale phosphoproteomic studies in plants have consistently found that RNA splicing-related proteins are extensively phosphorylated, however, the signaling pathways involved in AS regulation have not been resolved. In this mini-review, we summarize our current knowledge of the three major splicing-related protein kinase families in plants that are suggested to mediate AS phospho-regulation and draw comparisons to their metazoan orthologs. We also summarize and contextualize the phosphorylation events identified as occurring on splicing-related protein families to illustrate the high degree to which splicing-related proteins are modified, placing a new focus on elucidating the impacts of AS at the protein and PTM-level.
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Affiliation(s)
| | - R. Glen Uhrig
- University of Alberta, Department of Biological Sciences, Edmonton, AB, Canada
- University of Alberta, Department of Biochemistry, Edmonton, AB, Canada
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4
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Araki S, Ohori M, Yugami M. Targeting pre-mRNA splicing in cancers: roles, inhibitors, and therapeutic opportunities. Front Oncol 2023; 13:1152087. [PMID: 37342192 PMCID: PMC10277747 DOI: 10.3389/fonc.2023.1152087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 05/09/2023] [Indexed: 06/22/2023] Open
Abstract
Accumulating evidence has indicated that pre-mRNA splicing plays critical roles in a variety of physiological processes, including development of multiple diseases. In particular, alternative splicing is profoundly involved in cancer progression through abnormal expression or mutation of splicing factors. Small-molecule splicing modulators have recently attracted considerable attention as a novel class of cancer therapeutics, and several splicing modulators are currently being developed for the treatment of patients with various cancers and are in the clinical trial stage. Novel molecular mechanisms modulating alternative splicing have proven to be effective for treating cancer cells resistant to conventional anticancer drugs. Furthermore, molecular mechanism-based combination strategies and patient stratification strategies for cancer treatment targeting pre-mRNA splicing must be considered for cancer therapy in the future. This review summarizes recent progress in the relationship between druggable splicing-related molecules and cancer, highlights small-molecule splicing modulators, and discusses future perspectives of splicing modulation for personalized and combination therapies in cancer treatment.
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5
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Aubol BE, Adams JA. SRPK1 regulates RNA binding in a pre-spliceosomal complex using a catalytic bypass mechanism. FEBS J 2022; 289:7428-7445. [PMID: 35730996 DOI: 10.1111/febs.16560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 05/10/2022] [Accepted: 06/21/2022] [Indexed: 01/14/2023]
Abstract
Serine-arginine protein kinase 1 (SRPK1) phosphorylates serine-arginine (SR) proteins in the cytoplasm, directing them to the nucleus for splicing function. SRPK1 has also been detected in the nucleus but its function here is still not fully understood. We now demonstrate that nuclear SRPK1 can regulate U1-70K, a protein component of the uridine-rich 1 small nuclear ribonucleoprotein (U1 snRNP) that binds SR proteins and facilitates 5' splice-site selection in precursor mRNA. We found that SRPK1 uses a large, disordered domain to bind U1-70K, regulating the interaction of an exonic splicing enhancer (ESE) to the associated SR protein. Surprisingly, the catalytic activity of SRPK1 is not required for this phenomenon. Instead, SRPK1 associates directly with the N-terminus of U1-70K and alters the regulatory function of the distal C-terminus, modifying interactions between the U1-70K:SR protein complex and the ESE. Disruption of SRPK1 binding to this complex affects the alternative splicing of genes modulated by the C-terminus of U1-70K. Such findings suggest that, in addition to operating as a traditional serine-modifying catalyst, SRPK1 can also bypass this intrinsic activity to regulate RNA contacts in an early pre-spliceosomal complex.
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Affiliation(s)
- Brandon E Aubol
- Department of Pharmacology, University of California San Diego, La Jolla, CA, USA
| | - Joseph A Adams
- Department of Pharmacology, University of California San Diego, La Jolla, CA, USA
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LIMK2 promotes the metastatic progression of triple-negative breast cancer by activating SRPK1. Oncogenesis 2020; 9:77. [PMID: 32859889 PMCID: PMC7455732 DOI: 10.1038/s41389-020-00263-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 08/10/2020] [Accepted: 08/17/2020] [Indexed: 12/21/2022] Open
Abstract
Triple-negative breast cancer (TNBC) is a highly metastatic breast cancer subtype and due to the lack of hormone receptors and HER2 expression, TNBC has limited therapeutic options with chemotherapy being the primary choice for systemic therapy. LIM Domain Kinase 2 (LIMK2) is a serine/threonine kinase that plays an important role in the regulation of actin filament dynamics. Here, we show that LIM domain kinase 2 (LIMK2) is overexpressed in TNBC, and short-hairpin RNA (shRNA)-mediated LIMK2 knockdown or its pharmacological inhibition blocks metastatic attributes of TNBC cells. To determine the mechanism by which LIMK2 promotes TNBC metastatic progression, we performed stable isotope labeling by amino acids in cell culture (SILAC) based unbiased large-scale phosphoproteomics analysis. This analysis identified 258 proteins whose phosphorylation was significantly reduced due to LIMK2 inhibition. Among these proteins, we identified SRSF protein kinase 1 (SRPK1), which encodes for a serine/arginine protein kinase specific for the SR (serine/arginine-rich domain) family of splicing factors. We show that LIMK2 inhibition blocked SRPK1 phosphorylation and consequentially its activity. Furthermore, similar to LIMK2, genetic inhibition of SRPK1 by shRNAs or its pharmacological inhibition blocked the metastatic attributes of TNBC cells. Moreover, the pharmacological inhibition of LIMK2 blocked metastatic progression in mice without affecting primary tumor growth. In sum, these results identified LIMK2 as a facilitator of distal TNBC metastasis and a potential target for preventing TNBC metastatic progression.
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Yang Q, Zhao J, Zhang W, Chen D, Wang Y. Aberrant alternative splicing in breast cancer. J Mol Cell Biol 2019; 11:920-929. [PMID: 31065692 PMCID: PMC6884705 DOI: 10.1093/jmcb/mjz033] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 02/19/2019] [Accepted: 03/03/2019] [Indexed: 12/11/2022] Open
Abstract
Alternative splicing is critical for human gene expression regulation, which plays a determined role in expanding the diversity of functional proteins. Importantly, alternative splicing is a hallmark of cancer and a potential target for cancer therapeutics. Based on the statistical data, breast cancer is one of the top leading causes of cancer-related deaths in women worldwide. Strikingly, alternative splicing is closely associated with breast cancer development. Here, we seek to provide a general review of the relationship between alternative splicing and breast cancer. We introduce the process of alternative splicing and its regulatory role in cancers. In addition, we highlight the functions of aberrant alternative splicing and mutations of splicing factors in breast cancer progression. Moreover, we discuss the role of alternative splicing in cancer drug resistance and the potential of being targets for cancer therapeutics.
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Affiliation(s)
- Quan Yang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian 116044, China
| | - Jinyao Zhao
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian 116044, China
| | - Wenjing Zhang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian 116044, China
| | - Dan Chen
- Department of Pathology, First Affiliated Hospital, Dalian Medical University, Dalian 116044, China
| | - Yang Wang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian 116044, China
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8
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Abstract
This work demonstrates that the outer mitochondrial-anchored [2Fe-2S] mitoNEET is able to bind within the central cavity of the voltage-dependent anion channel (VDAC) and regulate its gating in a redox-dependent manner. These findings have implications for ferroptosis, apoptosis, and iron metabolism by linking VDAC function, mitoNEET, and the redox environment of the cell. Furthermore, these findings introduce a potential player to the many mechanisms that may alter VDAC’s governance in times of homeostasis or strife. MitoNEET is an outer mitochondrial membrane protein essential for sensing and regulation of iron and reactive oxygen species (ROS) homeostasis. It is a key player in multiple human maladies including diabetes, cancer, neurodegeneration, and Parkinson’s diseases. In healthy cells, mitoNEET receives its clusters from the mitochondrion and transfers them to acceptor proteins in a process that could be altered by drugs or during illness. Here, we report that mitoNEET regulates the outer-mitochondrial membrane (OMM) protein voltage-dependent anion channel 1 (VDAC1). VDAC1 is a crucial player in the cross talk between the mitochondria and the cytosol. VDAC proteins function to regulate metabolites, ions, ROS, and fatty acid transport, as well as function as a “governator” sentry for the transport of metabolites and ions between the cytosol and the mitochondria. We find that the redox-sensitive [2Fe-2S] cluster protein mitoNEET gates VDAC1 when mitoNEET is oxidized. Addition of the VDAC inhibitor 4,4′-diisothiocyanatostilbene-2,2′-disulfonate (DIDS) prevents both mitoNEET binding in vitro and mitoNEET-dependent mitochondrial iron accumulation in situ. We find that the DIDS inhibitor does not alter the redox state of MitoNEET. Taken together, our data indicate that mitoNEET regulates VDAC in a redox-dependent manner in cells, closing the pore and likely disrupting VDAC’s flow of metabolites.
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9
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Barbosa ÉDAA, Seraphim TV, Gandin CA, Teixeira LF, da Silva RAG, Righetto GL, Goncalves KDA, Vasconcellos RDS, Almeida MR, Silva Júnior A, Fietto JLR, Kobarg J, Gileadi C, Massirer KB, Borges JC, de Oliveira Neto M, Bressan GC. Insights into the full-length SRPK2 structure and its hydrodynamic behavior. Int J Biol Macromol 2019; 137:205-214. [PMID: 31229549 DOI: 10.1016/j.ijbiomac.2019.06.135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 06/04/2019] [Accepted: 06/19/2019] [Indexed: 11/30/2022]
Abstract
The serine/arginine-rich protein kinase 2 (SRPK2) has been reported as upregulated in several cancer types, with roles in hallmarks such as cell migration, growth, and apoptosis. These findings have indicated that SRPK2 is a promising emerging target in drug discovery initiatives. Although high-resolution models are available for SRPK2 (PDB 2X7G), they have been obtained with a heavily truncated recombinant protein version (~50% of the primary structure), due to the presence of long intrinsically unstructured regions. In the present work, we sought to characterize the structure of a full-length recombinant version of SRPK2 in solution. Low-resolution Small-Angle X-ray Scattering data were obtained for both versions of SRPK2. The truncated ΔNΔS-SRPK2 presented a propensity to dimerize at higher concentrations whereas the full-length SRPK2 was mainly found as dimers. The hydrodynamic behavior of the full-length SRPK2 was further investigated by analytical size exclusion chromatography and sedimentation velocity analytical ultracentrifugation experiments. SRPK2 behaved as a monomer-dimer equilibrium and both forms have an elongated shape in solution, pointing to a stretched-to-closed tendency among the conformational plasticity observed. Taken together, these findings allowed us to define unique structural features of the SRPK2 within SRPK family, characterized by its flexible regions outside the bipartite kinase domain.
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Affiliation(s)
| | | | - César Augusto Gandin
- Departamento de Física e Biofísica, Universidade Estadual Paulista, Botucatu, SP, Brazil
| | | | | | - Germanna L Righetto
- Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | - Kaliandra De Almeida Goncalves
- Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | | | - Márcia Rogéria Almeida
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | | | | | - Jörg Kobarg
- Instituto de Biologia, Departamento de Bioquímica e Biologia Tecidual e Faculdade de Ciências Farmacêuticas, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | - Carina Gileadi
- Structural Genomics Consortium, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz, Av. Dr. André Tosello, 550, Barão Geraldo, Campinas, SP, Brazil; Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Katlin B Massirer
- Structural Genomics Consortium, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz, Av. Dr. André Tosello, 550, Barão Geraldo, Campinas, SP, Brazil; Center for Molecular Biology and Genetic Engineering, CBMEG, Universidade Estadual de Campinas, Campinas, SPUniversidade Estadual de Campinas, Campinas, Brazil
| | - Julio César Borges
- Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
| | - Mario de Oliveira Neto
- Departamento de Física e Biofísica, Universidade Estadual Paulista, Botucatu, SP, Brazil
| | - Gustavo Costa Bressan
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
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Antimetastatic effect of the pharmacological inhibition of serine/arginine-rich protein kinases (SRPK) in murine melanoma. Toxicol Appl Pharmacol 2018; 356:214-223. [DOI: 10.1016/j.taap.2018.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 08/14/2018] [Accepted: 08/17/2018] [Indexed: 02/06/2023]
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11
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Wang G, Sun P, Gong Z, Gu L, Lou Y, Fang W, Zhang L, Su L, Yang T, Wang B, Zhou J, Xu JR, Wang Z, Zheng W. Srk1 kinase, a SR protein-specific kinase, is important for sexual reproduction, plant infection and pre-mRNA processing in Fusarium graminearum. Environ Microbiol 2018; 20:3261-3277. [DOI: 10.1111/1462-2920.14299] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Revised: 05/24/2018] [Accepted: 05/26/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Guanghui Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
- Institute of Oceanography; Minjiang University; Fuzhou China
| | - Peng Sun
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Ziwen Gong
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Lianfeng Gu
- Basic Forestry and Proteomics Center (BFPC), Haixia Institute of Science and Technology; Fujian Agriculture and Forestry University; Fuzhou China
| | - Yi Lou
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Wenqin Fang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Lianhu Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Li Su
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Tao Yang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Baohua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
| | - Jie Zhou
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins; College of Life Sciences, Fujian Agriculture and Forestry University; Fuzhou China
| | - Jin-Rong Xu
- State Key Laboratory of Crop Stress Biology for Arid Areas; College of Plant Protection, Northwest A&F University; Yangling Shaanxi China
| | - Zonghua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
- Institute of Oceanography; Minjiang University; Fuzhou China
| | - Wenhui Zheng
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops; College of Plant Protection, Fujian Agriculture and Forestry University; Fuzhou China
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Bates DO, Morris JC, Oltean S, Donaldson LF. Pharmacology of Modulators of Alternative Splicing. Pharmacol Rev 2017; 69:63-79. [PMID: 28034912 PMCID: PMC5226212 DOI: 10.1124/pr.115.011239] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
More than 95% of genes in the human genome are alternatively spliced to form multiple transcripts, often encoding proteins with differing or opposing function. The control of alternative splicing is now being elucidated, and with this comes the opportunity to develop modulators of alternative splicing that can control cellular function. A number of approaches have been taken to develop compounds that can experimentally, and sometimes clinically, affect splicing control, resulting in potential novel therapeutics. Here we develop the concepts that targeting alternative splicing can result in relatively specific pathway inhibitors/activators that result in dampening down of physiologic or pathologic processes, from changes in muscle physiology to altering angiogenesis or pain. The targets and pharmacology of some of the current inhibitors/activators of alternative splicing are demonstrated and future directions discussed.
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Affiliation(s)
- David O Bates
- Cancer Biology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (D.O.B.); School of Chemistry, UNSW Australia, Sydney, Australia (J.C.M.); School of Physiology, Pharmacology and Neurosciences, School of Clinical Sciences/Bristol Renal, University of Bristol, Bristol, United Kingdom (S.O.); and School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (L.F.D.)
| | - Jonathan C Morris
- Cancer Biology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (D.O.B.); School of Chemistry, UNSW Australia, Sydney, Australia (J.C.M.); School of Physiology, Pharmacology and Neurosciences, School of Clinical Sciences/Bristol Renal, University of Bristol, Bristol, United Kingdom (S.O.); and School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (L.F.D.)
| | - Sebastian Oltean
- Cancer Biology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (D.O.B.); School of Chemistry, UNSW Australia, Sydney, Australia (J.C.M.); School of Physiology, Pharmacology and Neurosciences, School of Clinical Sciences/Bristol Renal, University of Bristol, Bristol, United Kingdom (S.O.); and School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (L.F.D.)
| | - Lucy F Donaldson
- Cancer Biology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (D.O.B.); School of Chemistry, UNSW Australia, Sydney, Australia (J.C.M.); School of Physiology, Pharmacology and Neurosciences, School of Clinical Sciences/Bristol Renal, University of Bristol, Bristol, United Kingdom (S.O.); and School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (L.F.D.)
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13
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Koutroumani M, Papadopoulos GE, Vlassi M, Nikolakaki E, Giannakouros T. Evidence for disulfide bonds in SR Protein Kinase 1 (SRPK1) that are required for activity and nuclear localization. PLoS One 2017; 12:e0171328. [PMID: 28166275 PMCID: PMC5293202 DOI: 10.1371/journal.pone.0171328] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/18/2017] [Indexed: 11/18/2022] Open
Abstract
Serine/arginine protein kinases (SRPKs) phosphorylate Arg/Ser dipeptide-containing proteins that play crucial roles in a broad spectrum of basic cellular processes. The existence of a large internal spacer sequence that separates the bipartite kinase catalytic core is a unique structural feature of SRPKs. Previous structural studies on a catalytically active fragment of SRPK1, which lacks the main part of the spacer domain, revealed that SRPK1 remains in an active state without any post-translational modifications or specific intra-protein interactions, while the spacer domain is depicted as a loop structure, outside the kinase core. Using systematic mutagenesis we now provide evidence that replacement of any individual cysteine residue in the spacer, apart from Cys414, or in its proximal flaking ends of the two kinase catalytic domains has an impact on kinase activity. Furthermore, the cysteine residues are critical for nuclear translocation of SRPK1 in response to genotoxic stress and SRPK1-dependent splicing of a reporter gene. While replacement of Cys207, Cys502 and Cys539 of the catalytic domains is predicted to distort the kinase active structure, our findings suggest that Cys356, Cys386, Cys427 and Cys455 of the spacer domain and Cys188 of the first catalytic domain are engaged in disulfide bridging. We propose that such a network of intramolecular disulfide bonds mediates the bending of the spacer region thus allowing the proximal positioning of the two catalytic subunits which is a prerequisite for SRPK1 activity.
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Affiliation(s)
- Maria Koutroumani
- Laboratory of Biochemistry, Department of Chemistry, Aristotle University, Thessaloniki, Greece
| | | | - Metaxia Vlassi
- Institute of Biosciences & Applications, National Centre for Scientific Research "Demokritos", Athens, Greece
| | - Eleni Nikolakaki
- Laboratory of Biochemistry, Department of Chemistry, Aristotle University, Thessaloniki, Greece
- * E-mail: (TG); (EN)
| | - Thomas Giannakouros
- Laboratory of Biochemistry, Department of Chemistry, Aristotle University, Thessaloniki, Greece
- * E-mail: (TG); (EN)
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14
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Abstract
SR proteins are essential splicing factors that are regulated through multisite phosphorylation of their RS (arginine/serine-rich) domains by two major families of protein kinases. The SRPKs (SR-specific protein kinases) efficiently phosphorylate the arginine/serine dipeptides in the RS domain using a conserved docking groove in the kinase domain. In contrast, CLKs (Cdc2-like kinases) lack a docking groove and phosphorylate both arginine/serine and serine-proline dipeptides, modifications that generate a hyperphosphorylated state important for unique SR protein-dependent splicing activities. All CLKs contain long flexible N-terminal extensions (140-300 residues) that resemble the RS domains present in their substrate SR proteins. We showed that the N-terminus in CLK1 contacts both the kinase domain and the RS domain of the SR protein SRSF1 (SR protein splicing factor 1). This interaction not only is essential for facilitating hyperphosphorylation, but also induces co-operative binding of SRSF1 to RNA. The N-terminus of CLK1 enhances the total phosphoryl contents of a panel of physiological substrates including SRSF1, SRSF2, SRSF5 and Tra2β1 (transformer 2β1) by 2-3-fold. These findings suggest that CLK1-dependent hyperphosphorylation is the result of a general mechanism in which the N-terminus acts as a bridge connecting the kinase domain and the RS domain of the SR protein.
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15
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Aubol BE, Adams JA. Recruiting a silent partner for activation of the protein kinase SRPK1. Biochemistry 2014; 53:4625-34. [PMID: 24984036 PMCID: PMC4108178 DOI: 10.1021/bi500483m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The SRPK family of protein kinases regulates mRNA splicing by phosphorylating an essential group of factors known as SR proteins, so named for a C-terminal domain enriched in arginine-serine dipeptide repeats (RS domains). SRPKs phosphorylate RS domains at numerous sites altering SR protein subcellular localization and splicing function. The RS domains in these splicing factors differ considerably in overall length and dipeptide layout. Despite their importance, little is known about how these diverse RS domains interact with SRPKs and regulate SR protein phosphorylation. We now show that sequences distal to the SRPK1 consensus region in the RS domain of the prototype SR protein SRSF1 are not passive as originally thought but rather play active roles in accelerating phosphorylation rates. Located in the C-terminal end of the RS domain, this nonconsensus region up-regulates rate-limiting ADP release through the nucleotide release factor, a structural module in SRPK1 composed of two noncontiguous sequence elements outside the kinase core domain. The data show that the RS domain in SRSF1 is multifunctional and that sequences once thought to be catalytically silent can be recruited to enhance the efficiency of SR protein phosphorylation.
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Affiliation(s)
- Brandon E Aubol
- Department of Pharmacology, University of California, San Diego , La Jolla, California 92093-0636, United States
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Primary structural features of SR-like protein acinusS govern the phosphorylation mechanism by SRPK2. Biochem J 2014; 459:181-91. [PMID: 24444330 DOI: 10.1042/bj20131091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
SRPKs (serine/arginine protein kinases) are highly specific kinases that recognize and phosphorylate RS (Arg-Ser) dipeptide repeats. It has been shown previously that SRPK1 phosphorylates the RS domain of SRSF1 (serine/arginine splicing factor 1) at multiple sites using a directional and processive mechanism. Such ability to processively phosphorylate substrates is proposed to be an inherent characteristic of SRPKs. SRPK2 is highly related to SRPK1 in sequence and in vitro properties, yet it has been shown to have distinct substrate specificity and physiological function in vivo. To study the molecular basis for substrate specificity of SRPK2, we investigated the roles of the non-kinase regions and a conserved docking groove of SRPK2 in the recognition and phosphorylation of different substrates: SRSF1 and acinusS. Our results reveal that a conserved electronegative docking groove in SRPK2, but not its non-kinase regions, is responsible for substrate binding regardless of their identities. Although SRPK2 phosphorylates SRSF1 in a processive manner as predicted, an electronegative region on acinusS restricts SRPK2 phosphorylation to a single specific site despite the presence of multiple RS dipeptides. These results suggest that primary structural elements on the substrates serve as key regulatory roles in determining the phosphorylation mechanism of SRPK2.
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Abstract
Serine-arginine protein kinases 2 (SRPK2) is a cell cycle-regulated kinase that phosphorylates serine/arginine domain-containing proteins and mediates pre-mRNA splicing with unclear function in neurons. Here, we show that SRPK2 phosphorylates tau on S214, suppresses tau-dependent microtubule polymerization, and inhibits axonal elongation in neurons. Depletion of SRPK2 in dentate gyrus inhibits tau phosphorylation in APP/PS1 mouse and alleviates the impaired cognitive behaviors. The defective LTP in APP/PS1 mice is also improved after SRPK2 depletion. Moreover, active SRPK2 is increased in the cortex of APP/PS1 mice and the pathological structures of human Alzheimer's disease (AD) brain. Therefore, our study suggests SRPK2 may contribute to the formation of hyperphosphorylated tau and the pathogenesis of AD.
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Aubol BE, Plocinik RM, McGlone ML, Adams JA. Nucleotide release sequences in the protein kinase SRPK1 accelerate substrate phosphorylation. Biochemistry 2012; 51:6584-94. [PMID: 22839969 DOI: 10.1021/bi300876h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein kinases are essential signaling enzymes that transfer phosphates from bound ATP to select amino acids in protein targets. For most kinases, the phosphoryl transfer step is highly efficient, while the rate-limiting step for substrate processing involves slow release of the product ADP. It is generally thought that structural factors intrinsic to the kinase domain and the nucleotide-binding pocket control this step and consequently the efficiency of protein phosphorylation for these cases. However, the kinase domains of protein kinases are commonly flanked by sequences that regulate catalytic function. To address whether such sequences could alter nucleotide exchange and, thus, regulate protein phosphorylation, the presence of activating residues external to the kinase domain was probed in the serine protein kinase SRPK1. Deletion analyses indicate that a small segment of a large spacer insert domain and a portion of an N-terminal extension function cooperatively to increase nucleotide exchange. The data point to a new mode of protein kinase regulation in which select sequences outside the kinase domain constitute a nucleotide release factor that likely interacts with the small lobe of the kinase domain and enhances protein substrate phosphorylation through increases in ADP dissociation rate.
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Affiliation(s)
- Brandon E Aubol
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA
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