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Baldwin KT, Murai KK, Khakh BS. Astrocyte morphology. Trends Cell Biol 2024; 34:547-565. [PMID: 38180380 DOI: 10.1016/j.tcb.2023.09.006] [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: 07/13/2023] [Revised: 09/18/2023] [Accepted: 09/29/2023] [Indexed: 01/06/2024]
Abstract
Astrocytes are predominant glial cells that tile the central nervous system (CNS). A cardinal feature of astrocytes is their complex and visually enchanting morphology, referred to as bushy, spongy, and star-like. A central precept of this review is that such complex morphological shapes evolved to allow astrocytes to contact and signal with diverse cells at a range of distances in order to sample, regulate, and contribute to the extracellular milieu, and thus participate widely in cell-cell signaling during physiology and disease. The recent use of improved imaging methods and cell-specific molecular evaluations has revealed new information on the structural organization and molecular underpinnings of astrocyte morphology, the mechanisms of astrocyte morphogenesis, and the contributions to disease states of reduced morphology. These insights have reignited interest in astrocyte morphological complexity as a cornerstone of fundamental glial biology and as a critical substrate for multicellular spatial and physiological interactions in the CNS.
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Affiliation(s)
- Katherine T Baldwin
- Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Keith K Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada.
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90034, USA; Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90034, USA.
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Hara Y, Ichiraku A, Matsuda T, Sakane A, Sasaki T, Nagai T, Horikawa K. High-affinity tuning of single fluorescent protein-type indicators by flexible linker length optimization in topology mutant. Commun Biol 2024; 7:705. [PMID: 38851844 PMCID: PMC11162441 DOI: 10.1038/s42003-024-06394-0] [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: 05/17/2023] [Accepted: 05/29/2024] [Indexed: 06/10/2024] Open
Abstract
Genetically encoded Ca2+ indicators (GECIs) are versatile for live imaging of cellular activities. Besides the brightness and dynamic range of signal change of GECIs, Ca2+ affinity is another critical parameter for successful Ca2+ imaging, as the concentration range of Ca2+ dynamics differs from low nanomolar to sub-millimolar depending on the celltype and organism. However, ultrahigh-affinity GECIs, particularly the single fluorescent protein (1FP)-type, are lacking. Here, we report a simple strategy that increases Ca2+ affinity through the linker length optimization in topology mutants of existing 1FP-type GECIs. The resulting ultrahigh-affinity GECIs, CaMPARI-nano, BGECO-nano, and RCaMP-nano (Kd = 17-25 nM), enable unique biological applications, including the detection of low nanomolar Ca2+ dynamics, highlighting active signaling cells, and multi-functional imaging with other second messengers. The linker length optimization in topology mutants could be applied to other 1FP-type indicators of glutamate and potassium, rendering it a widely applicable technique for modulating indicator affinity.
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Affiliation(s)
- Yusuke Hara
- Department of Optical Imaging, Advanced Research Promotion Center, Tokushima University, 3-18-15 Kuramoto, Tokushima, Tokushima, 770-8503, Japan
| | - Aya Ichiraku
- Department of Optical Imaging, Advanced Research Promotion Center, Tokushima University, 3-18-15 Kuramoto, Tokushima, Tokushima, 770-8503, Japan
| | - Tomoki Matsuda
- Department of Biomolecular Science and Engineering, SANKEN, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan
| | - Ayuko Sakane
- Department of Biochemistry, Tokushima University Graduate School of Medicine, 3-18-15 Kuramoto, Tokushima, Tokushima, 770-8503, Japan
- Division of Interdisciplinary Researches for Medicine and Photonics, Institute of Post-LED Photonics (pLED), Tokushima University, 3-18-15 Kuramoto, Tokushima, Tokushima, 770-8503, Japan
| | - Takuya Sasaki
- Department of Biochemistry, Tokushima University Graduate School of Medicine, 3-18-15 Kuramoto, Tokushima, Tokushima, 770-8503, Japan
| | - Takeharu Nagai
- Department of Biomolecular Science and Engineering, SANKEN, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan
- Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan
| | - Kazuki Horikawa
- Department of Optical Imaging, Advanced Research Promotion Center, Tokushima University, 3-18-15 Kuramoto, Tokushima, Tokushima, 770-8503, Japan.
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Kameyama T, Miyata M, Shiotani H, Adachi J, Kakuta S, Uchiyama Y, Mizutani K, Takai Y. Heterogeneity of perivascular astrocyte endfeet depending on vascular regions in the mouse brain. iScience 2023; 26:108010. [PMID: 37829206 PMCID: PMC10565786 DOI: 10.1016/j.isci.2023.108010] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 07/14/2023] [Accepted: 09/18/2023] [Indexed: 10/14/2023] Open
Abstract
Astrocytes interact with not only synapses but also brain blood vessels through perivascular astrocyte endfeet (PV-AEF) to form the neurovascular unit (NVU). However, PV-AEF components have not been fully identified. Here, we biochemically isolated blood vessels from mouse brain homogenates and purified PV-AEF. The purified PV-AEF were observed in different sizes, similar to PV-AEF on brain blood vessels. Mass spectrometry analysis identified 9,762 proteins in the purified PV-AEF, including cell adhesion molecules, nectin-2δ, Kirrel2, and podoplanin. Immunofluorescence microscopic analysis revealed that nectin-2δ and podoplanin were concentrated mainly in arteries/arterioles and veins/venules of the mouse brain, whereas Kirrel2 was mainly in arteries/arterioles. Nectin-2α/δ, Kirrel2, and podoplanin were preferentially observed in large sizes of the purified PV-AEF. Furthermore, Kirrel2 potentially has cell adhesion activity of cultured astrocytes. Collectively, these results indicate that PV-AEF have heterogeneity in sizes and molecular components, implying different roles of PV-AEF in NVU function depending on vascular regions.
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Affiliation(s)
- Takeshi Kameyama
- Division of Pathogenetic Signaling, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan
- Department of Immunology and Parasitology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Muneaki Miyata
- Division of Pathogenetic Signaling, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan
- Division of Pathogenetic Signaling, Institute of Advanced Medical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Hajime Shiotani
- Division of Pathogenetic Signaling, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan
- Division of Pathogenetic Signaling, Institute of Advanced Medical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Jun Adachi
- Laboratory of Proteomics for Drug Discovery, Center for Drug Design Research, National Institute of Biomedical Innovation, Health and Nutrition, Osaka 567-0085, Japan
- Laboratory of Clinical and Analytical Chemistry, Center for Drug Design Research, National Institute of Biomedical Innovation, Health and Nutrition, Osaka 567-0085, Japan
| | - Soichiro Kakuta
- Laboratory of Morphology and Image Analysis, Biomedical Research Core Facilities, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Cellular Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
| | - Yasuo Uchiyama
- Department of Cellular Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
| | - Kiyohito Mizutani
- Division of Pathogenetic Signaling, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan
- Division of Pathogenetic Signaling, Institute of Advanced Medical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Yoshimi Takai
- Division of Pathogenetic Signaling, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan
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