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Ahmad M, Krüger BT, Kroll T, Vettorazzi S, Dorn AK, Mengele F, Lee S, Nandi S, Yilmaz D, Stolz M, Tangudu NK, Vázquez DC, Pachmayr J, Cirstea IC, Spasic MV, Ploubidou A, Ignatius A, Tuckermann J. Inhibition of Cdk5 increases osteoblast differentiation and bone mass and improves fracture healing. Bone Res 2022; 10:33. [PMID: 35383146 PMCID: PMC8983726 DOI: 10.1038/s41413-022-00195-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [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] [Received: 04/14/2021] [Revised: 12/10/2021] [Accepted: 12/21/2021] [Indexed: 11/09/2022] Open
Abstract
Identification of regulators of osteoblastogenesis that can be pharmacologically targeted is a major goal in combating osteoporosis, a common disease of the elderly population. Here, unbiased kinome RNAi screening in primary murine osteoblasts identified cyclin-dependent kinase 5 (Cdk5) as a suppressor of osteoblast differentiation in both murine and human preosteoblastic cells. Cdk5 knockdown by siRNA, genetic deletion using the Cre-loxP system, or inhibition with the small molecule roscovitine enhanced osteoblastogenesis in vitro. Roscovitine treatment significantly enhanced bone mass by increasing osteoblastogenesis and improved fracture healing in mice. Mechanistically, downregulation of Cdk5 expression increased Erk phosphorylation, resulting in enhanced osteoblast-specific gene expression. Notably, simultaneous Cdk5 and Erk depletion abrogated the osteoblastogenesis conferred by Cdk5 depletion alone, suggesting that Cdk5 regulates osteoblast differentiation through MAPK pathway modulation. We conclude that Cdk5 is a potential therapeutic target to treat osteoporosis and improve fracture healing.
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Affiliation(s)
- Mubashir Ahmad
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany.,Institute of Orthopedic Research and Biomechanics, Ulm University, Helmholtzstrasse 14, 89081, Ulm, Germany
| | - Benjamin Thilo Krüger
- Institute of Orthopedic Research and Biomechanics, Ulm University, Helmholtzstrasse 14, 89081, Ulm, Germany
| | - Torsten Kroll
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstrasse 11, D-07745, Jena, Germany
| | - Sabine Vettorazzi
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Ann-Kristin Dorn
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Florian Mengele
- Praxisklinik für Orthopädie, Unfall- und Neurochirurgie Prof. Bischoff/Dr. Spies/Dr. Mengele, 89231, Neu-Ulm, Germany
| | - Sooyeon Lee
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Sayantan Nandi
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Dilay Yilmaz
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Miriam Stolz
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Naveen Kumar Tangudu
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany.,UPMC Hillman Cancer Center, Department of Pharmacology and Chemical Biology, University of Pittsburgh, 5115 Center Avenue, 15232, Pittsburgh, PA, USA
| | - David Carro Vázquez
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany.,TAmiRNA GmbH, Leberstrasse 20, 1110, Vienna, Austria
| | - Johanna Pachmayr
- Paracelsus Medizinische Privatuniverstät, Institute of Pharmacy, Strubergasse 21, 5020, Salzburg, Austria
| | - Ion Cristian Cirstea
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Maja Vujic Spasic
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany
| | - Aspasia Ploubidou
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstrasse 11, D-07745, Jena, Germany
| | - Anita Ignatius
- Institute of Orthopedic Research and Biomechanics, Ulm University, Helmholtzstrasse 14, 89081, Ulm, Germany
| | - Jan Tuckermann
- Institute of Comparative Molecular Endocrinology (CME), Ulm University, Helmholtzstrasse 8/1, 89081, Ulm, Germany. .,Department of Endocrinology, Ludwig Maximilians University Munich, Munich, 80336, Germany.
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Zhan A, Xu X, Chen L, Wang X, Yanfeng X, Dan W, Zhan Y, Shi Q. Decreased expression of Gab2 in patients with temporal lobe epilepsy and pilocarpine-induced rat model. Synapse 2013; 68:168-77. [PMID: 24327320 DOI: 10.1002/syn.21725] [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] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 11/24/2013] [Accepted: 12/04/2013] [Indexed: 12/30/2022]
Abstract
Growth factor receptor bound protein-2 associated binding protein-2 (Gab2) is widely expressed in the central nervous system, and participates in multiple signaling pathways. Recent studies showed that Gab2 was involved in the pathogenesis of Alzheimer's disease (AD). Gab2 reduces tau phosphorylation levels and is associated with cellular apoptosis and differentiation. However, whether Gab2 was also involved in the pathogenesis of epilepsy, remains unknown. This study aimed to investigate the expression pattern of Gab2 protein in brains with temporal lobe epilepsy (TLE) and in pilocarpine-induced rat model of TLE. Western blot, immunohistochemistry, and immunofluorescence were used to assess the location and the expression level of Gab2 in the neocortex of the temporal lobe in patients with TLE and in rat model of epilepsy. Results showed that Gab2 protein was expressed mainly in the membranes and cytoplasm of neurons in the cortex and hippocampus. Gab2 protein expression was remarkably reduced in temporal neocortex of TLE patients. In hippocampus and adjacent cortex in rat epilepsy model, Gab2 expression was decreased at different time points after kindling compared with the controls, and the lowest level of Gab2 expression occurred at 1 week. Thus, significant reductions of Gab2 protein in both TLE patients and epilepsy rats suggest that Gab2 may play an important role in the pathogenesis of TLE.
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Affiliation(s)
- Ao Zhan
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
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Kesavapany S, Pareek TK, Zheng YL, Amin N, Gutkind JS, Ma W, Kulkarni AB, Grant P, Pant HC. Neuronal nuclear organization is controlled by cyclin-dependent kinase 5 phosphorylation of Ras Guanine nucleotide releasing factor-1. Neurosignals 2006; 15:157-73. [PMID: 16921254 DOI: 10.1159/000095130] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Accepted: 05/25/2006] [Indexed: 11/19/2022] Open
Abstract
RasGRF1 is a member of the Ras guanine nucleotide exchange factor (RasGEF) family of proteins which are directly responsible for the activation of Ras and Rac GTPases. Originally identified as a phosphoprotein, RasGRF1 has been shown to be phosphorylated by protein kinase A and more recently, by the non-receptor tyrosine kinases Ack1 and Src. In this report we show that RasGRF1 interacts with and is phosphorylated by Cdk5 on serine 731 to regulate its steady state levels in mammalian cells as well as in neurons. Phosphorylation on this site by Cdk5 leads to RasGRF1 degradation through a calpain-dependent mechanism. Additionally, cortical neurons from Cdk5 knockout mice have higher levels of RasGRF1 which are reduced when wild-type Cdk5 is transfected into these neurons. In mitotic cells, nuclei become disorganized when RasGRF1 is overexpressed and this is rescued when RasGRF1 is co-expressed with active Cdk5. When RasGRF1 levels are elevated in neurons through overexpression of either the wild-type RasGRF1, or the phosphorylation mutant of RasGRF1 and by the transfection of a dominant negative Cdk5 construct, nuclei appeared condensed and fragmented. On the other hand, a reduction of RasGRF1 levels through p35/Cdk5 overexpression also leads to nuclear condensation in neurons. These data show that phosphorylation of RasGRF1 by Cdk5 tightly regulates its levels, which is essential for proper cellular organization.
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Affiliation(s)
- Sashi Kesavapany
- Cytoskeletal Protein Regulation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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Tomizawa K, Sunada S, Lu YF, Oda Y, Kinuta M, Ohshima T, Saito T, Wei FY, Matsushita M, Li ST, Tsutsui K, Hisanaga SI, Mikoshiba K, Takei K, Matsui H. Cophosphorylation of amphiphysin I and dynamin I by Cdk5 regulates clathrin-mediated endocytosis of synaptic vesicles. J Cell Biol 2003; 163:813-24. [PMID: 14623869 PMCID: PMC2173686 DOI: 10.1083/jcb.200308110] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Accepted: 10/07/2003] [Indexed: 11/22/2022] Open
Abstract
It has been thought that clathrin-mediated endocytosis is regulated by phosphorylation and dephosphorylation of many endocytic proteins, including amphiphysin I and dynamin I. Here, we show that Cdk5/p35-dependent cophosphorylation of amphiphysin I and dynamin I plays a critical role in such processes. Cdk5 inhibitors enhanced the electric stimulation-induced endocytosis in hippocampal neurons, and the endocytosis was also enhanced in the neurons of p35-deficient mice. Cdk5 phosphorylated the proline-rich domain of both amphiphysin I and dynamin I in vitro and in vivo. Cdk5-dependent phosphorylation of amphiphysin I inhibited the association with beta-adaptin. Furthermore, the phosphorylation of dynamin I blocked its binding to amphiphysin I. The phosphorylation of each protein reduced the copolymerization into a ring formation in a cell-free system. Moreover, the phosphorylation of both proteins completely disrupted the copolymerization into a ring formation. Finally, phosphorylation of both proteins was undetectable in p35-deficient mice.
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Affiliation(s)
- Kazuhito Tomizawa
- Department of Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan.
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Tomizawa K, Ohta J, Matsushita M, Moriwaki A, Li ST, Takei K, Matsui H. Cdk5/p35 regulates neurotransmitter release through phosphorylation and downregulation of P/Q-type voltage-dependent calcium channel activity. J Neurosci 2002; 22:2590-7. [PMID: 11923424 DOI: 20026252] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase with close structural homology to the mitotic Cdks. The complex of Cdk5 and p35, the neuron-specific regulatory subunit of Cdk5, plays important roles in brain development, such as neuronal migration and neurite outgrowth. Moreover, Cdk5 is thought to be involved in the promotion of neurodegeneration in Alzheimer's disease. Cdk5 is abundant in mature neurons; however, its physiological functions in the adult brain are unknown. Here we show that Cdk5/p35 regulates neurotransmitter release in the presynaptic terminal. Both Cdk5 and p35 were abundant in the synaptosomes. Roscovitine, a specific inhibitor of Cdk5 in neurons, induced neurotransmitter release from the synaptosomes in response to membrane depolarization and enhanced the EPSP slopes in rat hippocampal slices. The electrophysiological study using each specific inhibitor of the voltage-dependent calcium channels (VDCCs) and calcium imaging revealed that roscovitine enhanced Ca2+ influx from the P/Q-type VDCC. Moreover, Cdk5/p25 phosphorylated the intracellular loop connecting domains II and III (L(II-III)) between amino acid residues 724 and 981 of isoforms cloned from rat brain of the alpha1A subunit of P/Q-type Ca2+ channels. The phosphorylation inhibited the interaction of L(II-III) with SNAP-25 and synaptotagmin I, which were plasma membrane soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) proteins and were required for efficient neurotransmitter release. These results strongly suggest that Cdk5/p35 inhibits neurotransmitter release through the phosphorylation of P/Q-type VDCC and downregulation of the channel activity.
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