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Burg MG. Bill Pak: reflections on mentoring. J Neurogenet 2024:1-3. [PMID: 38975968 DOI: 10.1080/01677063.2024.2374054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 06/25/2024] [Indexed: 07/09/2024]
Affiliation(s)
- Martin G Burg
- Departments of Biomedical Sciences and Cell and Molecular Biology, Grand Valley State University, Allendale, MI, USA
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2
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Minke B. The pioneering use of the PDA phenotype by Bill Pak for screening a network of phototransduction genes and the associated signaling pathways. J Neurogenet 2024:1-7. [PMID: 38896419 DOI: 10.1080/01677063.2024.2335146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Accepted: 03/21/2024] [Indexed: 06/21/2024]
Affiliation(s)
- Baruch Minke
- Department of Medical Neurobiology, The Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine and the Edmond and Lily Safra Center for brain research (ELSC), The Hebrew University, Jerusalem, Israel
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3
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Ferng D, Sun W, Shieh BH. Differential activation of rhodopsin triggers distinct endocytic trafficking and recycling in vivo via differential phosphorylation. PLoS One 2024; 19:e0303882. [PMID: 38848405 PMCID: PMC11161057 DOI: 10.1371/journal.pone.0303882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 05/02/2024] [Indexed: 06/09/2024] Open
Abstract
Activated GPCRs are phosphorylated and internalized mostly via clathrin-mediated endocytosis (CME), which are then sorted for recycling or degradation. We investigated how differential activation of the same GPCR affects its endocytic trafficking in vivo using rhodopsin as a model in pupal photoreceptors of flies expressing mCherry-tagged rhodopsin 1 (Rh1-mC) or GFP-tagged arrestin 1 (Arr1-GFP). Upon blue light stimulation, activated Rh1 recruited Arr1-GFP to the rhabdomere, which became co-internalized and accumulated in cytoplasmic vesicles of photoreceptors. This internalization was eliminated in shits1 mutants affecting dynamin. Moreover, it was blocked by either rdgA or rdgB mutations affecting the PIP2 biosynthesis. Together, the blue light-initiated internalization of Rh1 and Arr1 belongs to CME. Green light stimulation also triggered the internalization and accumulation of activated Rh1-mC in the cytoplasm but with faster kinetics. Importantly, Arr1-GFP was also recruited to the rhabdomere but not co-internalized with Rh1-mC. This endocytosis was not affected in shits1 nor rdgA mutants, indicating it is not CME. We explored the fate of internalized Rh1-mC following CME and observed it remained in cytoplasmic vesicles following 30 min of dark adaptation. In contrast, in the non-CME Rh1-mC appeared readily recycled back to the rhabdomere within five min of dark treatment. This faster recycling may be regulated by rhodopsin phosphatase, RdgC. Together, we demonstrate two distinct endocytic and recycling mechanisms of Rh1 via two light stimulations. It appears that each stimulation triggers a distinct conformation leading to different phosphorylation patterns of Rh1 capable of recruiting Arr1 to rhabdomeres. However, a more stable interaction leads to the co-internalization of Arr1 that orchestrates CME. A stronger Arr1 association appears to impede the recycling of the phosphorylated Rh1 by preventing the recruitment of RdgC. We conclude that conformations of activated rhodopsin determine the downstream outputs upon phosphorylation that confers differential protein-protein interactions.
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Affiliation(s)
- Darwin Ferng
- Department of Pharmacology, Center for Molecular Neuroscience and Vision Research Center, Vanderbilt University, Nashville, TN, United States of America
| | - Wesley Sun
- Department of Pharmacology, Center for Molecular Neuroscience and Vision Research Center, Vanderbilt University, Nashville, TN, United States of America
| | - Bih-Hwa Shieh
- Department of Pharmacology, Center for Molecular Neuroscience and Vision Research Center, Vanderbilt University, Nashville, TN, United States of America
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4
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Pollard TD, Korn ED. Discovery of the first unconventional myosin: Acanthamoeba myosin-I. Front Physiol 2023; 14:1324623. [PMID: 38046947 PMCID: PMC10693453 DOI: 10.3389/fphys.2023.1324623] [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: 10/20/2023] [Accepted: 11/07/2023] [Indexed: 12/05/2023] Open
Abstract
Having characterized actin from Acanthamoeba castellanii (Weihing and Korn, Biochemistry, 1971, 10, 590-600) and knowing that myosin had been isolated from the slime mold Physarum (Hatano and Tazawa, Biochim. Biophys. Acta, 1968, 154, 507-519; Adelman and Taylor, Biochemistry, 1969, 8, 4976-4988), we set out in 1969 to find myosin in Acanthamoeba. We used K-EDTA-ATPase activity to assay myosin, because it is a unique feature of muscle myosins. After slightly less than 3 years, we purified a K-EDTA ATPase that interacted with actin. Actin filaments stimulated the Mg-ATPase activity of the crude enzyme, but this was lost with further purification. Recombining fractions from the column where this activity was lost revealed a "cofactor" that allowed actin filaments to stimulate the Mg-ATPase of the purified enzyme. The small size of the heavy chain and physical properties of the purified myosin were unprecedented, so many were skeptical, assuming that our myosin was a proteolytic fragment of a larger myosin similar to muscle or Physarum myosin. Subsequently our laboratories confirmed that Acanthamoeba myosin-I is a novel unconventional myosin that interacts with membrane lipids (Adams and Pollard, Nature, 1989, 340 (6234), 565-568) and that the cofactor is a myosin heavy chain kinase (Maruta and Korn, J. Biol. Chem., 1977, 252, 8329-8332). Phylogenetic analysis (Odronitz and Kollmar, Genome Biology, 2007, 8, R196) later established that class I myosin was the first myosin to appear during the evolution of eukaryotes.
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Affiliation(s)
- Thomas D. Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, United States
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, United States
| | - Edward D. Korn
- Scientist Emeritus, Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States
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Frequency and origin of the c.2090T>G p.(Leu697Trp) MYO3A variant associated with autosomal dominant hearing loss. Eur J Hum Genet 2022; 30:13-21. [PMID: 33953343 PMCID: PMC8738757 DOI: 10.1038/s41431-021-00891-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 03/15/2021] [Accepted: 04/08/2021] [Indexed: 02/07/2023] Open
Abstract
We recently described a novel missense variant [c.2090T>G:p.(Leu697Trp)] in the MYO3A gene, found in two Brazilian families with late-onset autosomal dominant nonsyndromic hearing loss (ADNSHL). Since then, with the objective of evaluating its contribution to ADNSHL in Brazil, the variant was screened in additional 101 pedigrees with probable ADNSHL without conclusive molecular diagnosis. The variant was found in three additional families, explaining 3/101 (~3%) of cases with ADNSHL in our Brazilian pedigree collection. In order to identify the origin of the variant, 21 individuals from the five families were genotyped with a high-density SNP array (~600 K SNPs- Axiom Human Origins; ThermoFisher). The identity by descent (IBD) approach revealed that many pairs of individuals from the different families have a kinship coefficient equivalent to that of second cousins, and all share a minimum haplotype of ~607 kb which includes the c.2090T>G variant suggesting it probably arose in a common ancestor. We inferred that the mutation occurred in a chromosomal segment of European ancestry and the time since the most common ancestor was estimated in 1100 years (CI = 775-1425). This variant was also reported in a Dutch family, which shares a 87,121 bp haplotype with the Brazilian samples, suggesting that Dutch colonists may have brought it to Northeastern Brazil in the 17th century. Therefore, the present study opens new avenues to investigate this variant not only in Brazilians but also in European families with ADNSHL.
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Waixenicin A, a marine-derived TRPM7 inhibitor: a promising CNS drug lead. Acta Pharmacol Sin 2020; 41:1519-1524. [PMID: 32994545 DOI: 10.1038/s41401-020-00512-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Accepted: 08/17/2020] [Indexed: 12/17/2022] Open
Abstract
Ion channels are the third largest class of targets for therapeutic drugs. The pharmacology of ion channels is an important research area for identifying new treatment options for human diseases. The past decade or so has seen increasing interest in an ion channel protein belonging to the transient receptor potential (TRP) family, namely the melastatin subfamily member 7 (TRPM7), as an emerging drug target. TRPM7 is a bifunctional protein with a magnesium and calcium-conducting divalent ion channel fused with an active kinase domain. TRPM7 is ubiquitously expressed in human tissues, including the brain, and regulates various cell biology processes such as magnesium and calcium homeostasis, cell growth and proliferation, and embryonic development. TRPM7 provides a link between cellular metabolic status and intracellular calcium homeostasis in neurons due to TRPM7's unique sensitivity to fluctuating intracellular Mg·ATP levels. Thus, the protein plays a key role in ischemic and hypoxic neuronal cell death and brain injury, and is one of the key nonglutamate mechanisms in cerebral ischemia and stroke. Currently, the most potent and specific TRPM7 inhibitor is waixenicin A, a xenicane diterpenoid from the Hawaiian soft coral Sarcothelia edmondsoni. Using waixenicin A as a pharmacological tool, we demonstrated that TRPM7 is involved in promoting neurite outgrowth in vitro. Most recently, we found that waixenicin A reduced hypoxic-ischemic brain injury and preserved long-term behavioral outcomes in mouse neonates. We here suggest that TRPM7 is an emerging drug target for CNS diseases and disorders, and waixenicin A is a viable drug lead for these disorders.
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Abstract
Myosins constitute a superfamily of actin-based molecular motor proteins that mediates a variety of cellular activities including muscle contraction, cell migration, intracellular transport, the formation of membrane projections, cell adhesion, and cell signaling. The 12 myosin classes that are expressed in humans share sequence similarities especially in the N-terminal motor domain; however, their enzymatic activities, regulation, ability to dimerize, binding partners, and cellular functions differ. It is becoming increasingly apparent that defects in myosins are associated with diseases including cardiomyopathies, colitis, glomerulosclerosis, neurological defects, cancer, blindness, and deafness. Here, we review the current state of knowledge regarding myosins and disease.
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Abstract
This book, a collection of chapters written by some of the leading researchers in the field of molecular motors, highlights the current understanding of the structure, molecular mechanism, and cellular roles of members of the myosin superfamily. Here, I briefly review the discovery of the first myosin motor, skeletal muscle myosin-II, and preview the contents of subsequent chapters.
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Affiliation(s)
- Lynne M Coluccio
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA, USA.
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9
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Liu X, Lin C, Sun L, Liu S, Sun J, Zhang L, Yang H. Transcriptome analysis of phototransduction-related genes in tentacles of the sea cucumber Apostichopus japonicus. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2020; 34:100675. [PMID: 32109670 DOI: 10.1016/j.cbd.2020.100675] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 02/14/2020] [Accepted: 02/15/2020] [Indexed: 11/18/2022]
Abstract
The sea cucumber Apostichopus japonicus (Selenka)is a typical nocturnal echinoderm, which is believed to be almost completely dependent on light intensity for the regulation of endogenous rhythms. Under conditions of high light intensity, this species shows clear evidence of light avoidance behavior, seeking out shaded areas of reef in which to reside. In this study, we performed RNA-Seq analysis to examine the tentacle transcriptome of A. japonicus specimens that had been subjected to dark and light (5 min and 1 h) conditions. We specifically focused on detecting genes involved in opsin-based light perception, including opsins and members of phototransduction-related pathways. On the basis of comparisons with both vertebrate and invertebrate phototransduction pathways, we determined that components of two of the main metazoan phototransduction pathways were altered in response to illumination. Among the key phototransduction-related genes in tentacles, we identified retinol dehydrogenase, members of the dehydrogenase/reductase family, and myosin III, and also detected a pair of visual pigment-like receptors, peropsin and peropsin-like, the homologous genes of which are believed to have the same function but show opposite expression patterns in response to different light environments. In general, the up-regulation of key genes in sea cucumber exposed to illumination indicated that the tentacles can respond to differences in the light environment at the molecular level.
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Affiliation(s)
- Xiaolu Liu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China; College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Chenggang Lin
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China; The Innovation of Seed Design, Chinese Academy of Sciences, Wuhan, 430071, PR China.
| | - Lina Sun
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Shilin Liu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Jingchun Sun
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Libin Zhang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Hongsheng Yang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China; The Innovation of Seed Design, Chinese Academy of Sciences, Wuhan, 430071, PR China
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10
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Ca2+ Signaling in Drosophila Photoreceptor Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:857-879. [DOI: 10.1007/978-3-030-12457-1_34] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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11
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Li C, Liu J, Lü P, Ma S, Zhu K, Gao L, Li B, Chen K. Identification, expression and function of myosin heavy chain family genes in Tribolium castaneum. Genomics 2019; 111:719-728. [DOI: 10.1016/j.ygeno.2018.04.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 04/12/2018] [Accepted: 04/13/2018] [Indexed: 02/07/2023]
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12
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Katz B, Minke B. The Drosophila light-activated TRP and TRPL channels - Targets of the phosphoinositide signaling cascade. Prog Retin Eye Res 2018; 66:200-219. [DOI: 10.1016/j.preteyeres.2018.05.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 04/29/2018] [Accepted: 05/02/2018] [Indexed: 01/28/2023]
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Li P, Wen Z, Zhang G, Zhang A, Fu X, Gao J. Knock-In Mice with Myo3a Y137C Mutation Displayed Progressive Hearing Loss and Hair Cell Degeneration in the Inner Ear. Neural Plast 2018; 2018:4372913. [PMID: 30123247 PMCID: PMC6079384 DOI: 10.1155/2018/4372913] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 05/28/2018] [Indexed: 12/02/2022] Open
Abstract
Myo3a is expressed in cochlear hair cells and retinal cells and is responsible for human recessive hereditary nonsyndromic deafness (DFNB30). To investigate the mechanism of DFNB30-type deafness, we established a mouse model of Myo3a kinase domain Y137C mutation by using CRISPR/Cas9 system. No difference in hearing between 2-month-old Myo3a mutant mice and wild-type mice was observed. The hearing threshold of the ≥6-month-old mutant mice was significantly elevated compared with that of the wild-type mice. We observed degeneration in the inner ear hair cells of 6-month-old Myo3a mutant mice, and the degeneration became more severe at the age of 12 months. We also found structural abnormality in the cochlear hair cell stereocilia. Our results showed that Myo3a is essential for normal hearing by maintaining the intact structure of hair cell stereocilia, and the kinase domain plays a critical role in the normal functions of Myo3a. This mouse line is an excellent model for studying DFNB30-type deafness in humans.
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Affiliation(s)
- Peipei Li
- School of Life Science, Shandong University, Jinan 250100, China
| | - Zongzhuang Wen
- School of Life Science, Shandong University, Jinan 250100, China
| | - Guangkai Zhang
- School of Life Science, Shandong University, Jinan 250100, China
| | - Aizhen Zhang
- School of Life Science, Shandong University, Jinan 250100, China
| | - Xiaolong Fu
- School of Life Science, Shandong University, Jinan 250100, China
| | - Jiangang Gao
- School of Life Science, Shandong University, Jinan 250100, China
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Davie K, Janssens J, Koldere D, De Waegeneer M, Pech U, Kreft Ł, Aibar S, Makhzami S, Christiaens V, Bravo González-Blas C, Poovathingal S, Hulselmans G, Spanier KI, Moerman T, Vanspauwen B, Geurs S, Voet T, Lammertyn J, Thienpont B, Liu S, Konstantinides N, Fiers M, Verstreken P, Aerts S. A Single-Cell Transcriptome Atlas of the Aging Drosophila Brain. Cell 2018; 174:982-998.e20. [PMID: 29909982 PMCID: PMC6086935 DOI: 10.1016/j.cell.2018.05.057] [Citation(s) in RCA: 437] [Impact Index Per Article: 72.8] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 03/30/2018] [Accepted: 05/25/2018] [Indexed: 02/06/2023]
Abstract
The diversity of cell types and regulatory states in the brain, and how these change during aging, remains largely unknown. We present a single-cell transcriptome atlas of the entire adult Drosophila melanogaster brain sampled across its lifespan. Cell clustering identified 87 initial cell clusters that are further subclustered and validated by targeted cell-sorting. Our data show high granularity and identify a wide range of cell types. Gene network analyses using SCENIC revealed regulatory heterogeneity linked to energy consumption. During aging, RNA content declines exponentially without affecting neuronal identity in old brains. This single-cell brain atlas covers nearly all cells in the normal brain and provides the tools to study cellular diversity alongside other Drosophila and mammalian single-cell datasets in our unique single-cell analysis platform: SCope (http://scope.aertslab.org). These results, together with SCope, allow comprehensive exploration of all transcriptional states of an entire aging brain. A single-cell atlas of the adult fly brain during aging Network inference reveals regulatory states related to oxidative phosphorylation Cell identity is retained during aging despite exponential decline of gene expression SCope: An online tool to explore and compare single-cell datasets across species
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Affiliation(s)
- Kristofer Davie
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Jasper Janssens
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Duygu Koldere
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Maxime De Waegeneer
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Uli Pech
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Neurosciences, KU Leuven, Leuven 3000, Belgium
| | - Łukasz Kreft
- VIB Bioinformatics Core, VIB, Ghent 9052, Belgium
| | - Sara Aibar
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Samira Makhzami
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Valerie Christiaens
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Carmen Bravo González-Blas
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | | | - Gert Hulselmans
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Katina I Spanier
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Thomas Moerman
- ESAT, KU Leuven, Leuven 3001, Belgium; Smart Applications and Innovation Services, IMEC, Leuven 3001, Belgium
| | | | - Sarah Geurs
- Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | - Thierry Voet
- Department of Human Genetics KU Leuven, Leuven 3000, Belgium
| | | | | | - Sha Liu
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Neurosciences, KU Leuven, Leuven 3000, Belgium
| | | | - Mark Fiers
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Neurosciences, KU Leuven, Leuven 3000, Belgium
| | - Patrik Verstreken
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Neurosciences, KU Leuven, Leuven 3000, Belgium
| | - Stein Aerts
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium; Department of Human Genetics KU Leuven, Leuven 3000, Belgium.
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Characterization of a novel MYO3A missense mutation associated with a dominant form of late onset hearing loss. Sci Rep 2018; 8:8706. [PMID: 29880844 PMCID: PMC5992146 DOI: 10.1038/s41598-018-26818-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 05/18/2018] [Indexed: 01/08/2023] Open
Abstract
Whole-exome sequencing of samples from affected members of two unrelated families with late-onset non-syndromic hearing loss revealed a novel mutation (c.2090 T > G; NM_017433) in MYO3A. The mutation was confirmed in 36 affected individuals, showing autosomal dominant inheritance. The mutation alters a single residue (L697W or p.Leu697Trp) in the motor domain of the stereocilia protein MYO3A, leading to a reduction in ATPase activity, motility, and an increase in actin affinity. MYO3A-L697W showed reduced filopodial actin protrusion initiation in COS7 cells, and a predominant tipward accumulation at filopodia and stereocilia when coexpressed with wild-type MYO3A and espin-1, an actin-regulatory MYO3A cargo. The combined higher actin affinity and duty ratio of the mutant myosin cause increased retention time at stereocilia tips, resulting in the displacement of the wild-type MYO3A protein, which may impact cargo transport, stereocilia length, and mechanotransduction. The dominant negative effect of the altered myosin function explains the dominant inheritance of deafness.
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Masters TA, Kendrick-Jones J, Buss F. Myosins: Domain Organisation, Motor Properties, Physiological Roles and Cellular Functions. Handb Exp Pharmacol 2017; 235:77-122. [PMID: 27757761 DOI: 10.1007/164_2016_29] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Myosins are cytoskeletal motor proteins that use energy derived from ATP hydrolysis to generate force and movement along actin filaments. Humans express 38 myosin genes belonging to 12 classes that participate in a diverse range of crucial activities, including muscle contraction, intracellular trafficking, cell division, motility, actin cytoskeletal organisation and cell signalling. Myosin malfunction has been implicated a variety of disorders including deafness, hypertrophic cardiomyopathy, Usher syndrome, Griscelli syndrome and cancer. In this chapter, we will first discuss the key structural and kinetic features that are conserved across the myosin family. Thereafter, we summarise for each member in turn its unique functional and structural adaptations, cellular roles and associated pathologies. Finally, we address the broad therapeutic potential for pharmacological interventions that target myosin family members.
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Affiliation(s)
- Thomas A Masters
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK.
| | | | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK
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Microenvironmental Gene Expression Plasticity Among Individual Drosophila melanogaster. G3-GENES GENOMES GENETICS 2016; 6:4197-4210. [PMID: 27770026 PMCID: PMC5144987 DOI: 10.1534/g3.116.035444] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Differences in phenotype among genetically identical individuals exposed to the same environmental condition are often noted in genetic studies. Despite this commonplace observation, little is known about the causes of this variability, which has been termed microenvironmental plasticity. One possibility is that stochastic or technical sources of variance produce these differences. A second possibility is that this variation has a genetic component. We have explored gene expression robustness in the transcriptomes of 730 individual Drosophila melanogaster of 16 fixed genotypes, nine of which are infected with Wolbachia. Three replicates of flies were grown, controlling for food, day/night cycles, humidity, temperature, sex, mating status, social exposure, and circadian timing of RNA extraction. Despite the use of inbred genotypes, and carefully controlled experimental conditions, thousands of genes were differentially expressed, revealing a unique and dynamic transcriptional signature for each individual fly. We found that 23% of the transcriptome was differentially expressed among individuals, and that the variability in gene expression among individuals is influenced by genotype. This transcriptional variation originated from specific gene pathways, suggesting a plastic response to the microenvironment; but there was also evidence of gene expression differences due to stochastic fluctuations. These observations reveal previously unappreciated genetic sources of variability in gene expression among individuals, which has implications for complex trait genetics and precision medicine.
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Qu R, Sang Q, Xu Y, Feng R, Jin L, He L, Wang L. Identification of a novel homozygous mutation in MYO3A in a Chinese family with DFNB30 non-syndromic hearing impairment. Int J Pediatr Otorhinolaryngol 2016; 84:43-7. [PMID: 27063751 DOI: 10.1016/j.ijporl.2016.02.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 02/25/2016] [Accepted: 02/26/2016] [Indexed: 10/22/2022]
Abstract
INTRODUCTION Hearing loss is a common sensory impairment. Several genetic loci or genes responsible for non-syndrome hearing loss have been identified, including the well-known deafness genes GJB2, MT-RNR1 and SLC26A4. MYO3A belongs to the myosin superfamily. Previously only three mutations in this gene have been found in an Isreali family with DFNB30, in which patients demonstrated progressive hearing loss. METHODS In this study, we characterized a consanguineous Kazakh family with congenital hearing loss. By targeted sequence capture and next-generation sequencing, we identified a homozygous mutation and did bioinformatics analysis to this mutation. RESULTS A homozygous mutation, MYO3A:c.1841C>T (p.S614F), was identified to be responsible for the disease. Ser614 is located in the motor domain of MYO3A that is highly conserved among different species. Molecular modeling predicts that the conserved Ser614 may play an important role in maintaining the stability of β-sheet and the interaction between neighboring β-strand. CONCLUSIONS This is the second report on MYO3A mutations in deafness and the first report in China. The finding help facilitate establishing a better relationship between MYO3A mutation and hearing phenotypes.
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Affiliation(s)
- Ronggui Qu
- State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Qing Sang
- State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Yao Xu
- State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Ruizhi Feng
- State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Li Jin
- State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China
| | - Lin He
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China; Bio-X Center, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai, China
| | - Lei Wang
- State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China.
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19
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Liu H, Li J, Raval MH, Yao N, Deng X, Lu Q, Nie S, Feng W, Wan J, Yengo CM, Liu W, Zhang M. Myosin III-mediated cross-linking and stimulation of actin bundling activity of Espin. eLife 2016; 5. [PMID: 26785147 PMCID: PMC4758956 DOI: 10.7554/elife.12856] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/18/2016] [Indexed: 11/13/2022] Open
Abstract
Class III myosins (Myo3) and actin-bundling protein Espin play critical roles in regulating the development and maintenance of stereocilia in vertebrate hair cells, and their defects cause hereditary hearing impairments. Myo3 interacts with Espin1 through its tail homology I motif (THDI), however it is not clear how Myo3 specifically acts through Espin1 to regulate the actin bundle assembly and stabilization. Here we discover that Myo3 THDI contains a pair of repeat sequences capable of independently and strongly binding to the ankyrin repeats of Espin1, revealing an unexpected Myo3-mediated cross-linking mechanism of Espin1. The structures of Myo3 in complex with Espin1 not only elucidate the mechanism of the binding, but also reveal a Myo3-induced release of Espin1 auto-inhibition mechanism. We also provide evidence that Myo3-mediated cross-linking can further promote actin fiber bundling activity of Espin1.
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Affiliation(s)
- Haiyang Liu
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Jianchao Li
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China
| | - Manmeet H Raval
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, United States
| | - Ningning Yao
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Xiaoying Deng
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Qing Lu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China
| | - Si Nie
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Wei Feng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jun Wan
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China.,Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China
| | - Christopher M Yengo
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, United States
| | - Wei Liu
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China.,Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China
| | - Mingjie Zhang
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China.,Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.,Center of Systems Biology and Human Health, School of Science and Institute for Advanced Study, Hong Kong University of Science and Technology, Hong Kong, China
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20
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Jaiswal M, Haelterman NA, Sandoval H, Xiong B, Donti T, Kalsotra A, Yamamoto S, Cooper TA, Graham BH, Bellen HJ. Impaired Mitochondrial Energy Production Causes Light-Induced Photoreceptor Degeneration Independent of Oxidative Stress. PLoS Biol 2015; 13:e1002197. [PMID: 26176594 PMCID: PMC4503542 DOI: 10.1371/journal.pbio.1002197] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/10/2015] [Indexed: 11/19/2022] Open
Abstract
Two insults often underlie a variety of eye diseases including glaucoma, optic atrophy, and retinal degeneration—defects in mitochondrial function and aberrant Rhodopsin trafficking. Although mitochondrial defects are often associated with oxidative stress, they have not been linked to Rhodopsin trafficking. In an unbiased forward genetic screen designed to isolate mutations that cause photoreceptor degeneration, we identified mutations in a nuclear-encoded mitochondrial gene, ppr, a homolog of human LRPPRC. We found that ppr is required for protection against light-induced degeneration. Its function is essential to maintain membrane depolarization of the photoreceptors upon repetitive light exposure, and an impaired phototransduction cascade in ppr mutants results in excessive Rhodopsin1 endocytosis. Moreover, loss of ppr results in a reduction in mitochondrial RNAs, reduced electron transport chain activity, and reduced ATP levels. Oxidative stress, however, is not induced. We propose that the reduced ATP level in ppr mutants underlies the phototransduction defect, leading to increased Rhodopsin1 endocytosis during light exposure, causing photoreceptor degeneration independent of oxidative stress. This hypothesis is bolstered by characterization of two other genes isolated in the screen, pyruvate dehydrogenase and citrate synthase. Their loss also causes a light-induced degeneration, excessive Rhodopsin1 endocytosis and reduced ATP without concurrent oxidative stress, unlike many other mutations in mitochondrial genes that are associated with elevated oxidative stress and light-independent photoreceptor demise. Some mitochondrial disorders cause blindness through increased oxidative stress. This study shows that in other such disorders, light-activated photoreceptors degenerate because the shortfall in mitochondrial energy production impairs rhodopsin trafficking and induces toxicity. Mitochondrial dysfunction is associated with a number of metabolic and neurological diseases such as Leigh syndrome and progressive blindness. Increased oxidative stress, which is often associated with mitochondrial dysfunction, is thought to be a common cause of disease progression. Here, we identified nuclear genes that encode mitochondrial proteins, whose loss causes the demise of photoreceptor neurons. Contrary to the common idea that this degeneration is triggered by elevated levels of oxidative stress, we find no change in the levels of oxidative stress. We show that activating photoreceptor neurons with light significantly increases energy production, and that this process is required to sustain their activity. Mitochondrial dysfunction impairs this capacity and leads to a premature termination of the light response. This in turn impairs the cycling of the light-sensitive receptor Rhodopsin in photoreceptors, and Rhodopsin accumulates in the cell inducing toxicity. This distinct mechanism of degeneration suggests that different mitochondrial diseases may follow different paths of disease progression and would hence respond differently to treatments.
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Affiliation(s)
- Manish Jaiswal
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
- Howard Hughes Medical Institute, BCM, Houston, Texas, United States of America
| | - Nele A. Haelterman
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
| | - Hector Sandoval
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
| | - Bo Xiong
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
| | - Taraka Donti
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
| | - Auinash Kalsotra
- Department of Pathology and Immunology, BCM, Houston, Texas, United States of America
| | - Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital (TCH), Houston, Texas, United States of America
| | - Thomas A. Cooper
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
- Department of Pathology and Immunology, BCM, Houston, Texas, United States of America
| | - Brett H. Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
| | - Hugo J. Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
- Howard Hughes Medical Institute, BCM, Houston, Texas, United States of America
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital (TCH), Houston, Texas, United States of America
- Department of Neuroscience, BCM, Houston, Texas, United States of America
- * E-mail:
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21
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Steele LD, Coates B, Valero MC, Sun W, Seong KM, Muir WM, Clark JM, Pittendrigh BR. Selective sweep analysis in the genomes of the 91-R and 91-C Drosophila melanogaster strains reveals few of the 'usual suspects' in dichlorodiphenyltrichloroethane (DDT) resistance. PLoS One 2015; 10:e0123066. [PMID: 25826265 PMCID: PMC4380341 DOI: 10.1371/journal.pone.0123066] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 02/17/2015] [Indexed: 11/19/2022] Open
Abstract
Adaptation of insect phenotypes for survival after exposure to xenobiotics can result from selection at multiple loci with additive genetic effects. To the authors' knowledge, no selective sweep analysis has been performed to identify such loci in highly dichlorodiphenyltrichloroethane (DDT) resistant insects. Here we compared a highly DDT resistant phenotype in the Drosophila melanogaster (Drosophila) 91-R strain to the DDT susceptible 91-C strain, both of common origin. Whole genome re-sequencing data from pools of individuals was generated separately for 91-R and 91-C, and mapped to the reference Drosophila genome assembly (v. 5.72). Thirteen major and three minor effect chromosome intervals with reduced nucleotide diversity (π) were identified only in the 91-R population. Estimates of Tajima's D (D) showed corresponding evidence of directional selection in these same genome regions of 91-R, however, no similar reductions in π or D estimates were detected in 91-C. An overabundance of non-synonymous proteins coding to synonymous changes were identified in putative open reading frames associated with 91-R. Except for NinaC and Cyp4g1, none of the identified genes were the 'usual suspects' previously observed to be associated with DDT resistance. Additionally, up-regulated ATP-binding cassette transporters have been previously associated with DDT resistance; however, here we identified a structurally altered MDR49 candidate resistance gene. The remaining fourteen genes have not previously been shown to be associated with DDT resistance. These results suggest hitherto unknown mechanisms of DDT resistance, most of which have been overlooked in previous transcriptional studies, with some genes having orthologs in mammals.
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Affiliation(s)
- Laura D. Steele
- Department of Entomology, University of Illinois, Urbana-Champaign, Illinois, United States of America
- * E-mail:
| | - Brad Coates
- United States Department of Agriculture, Agricultural Research Service, Corn Insects and Crop Genetics Research Unit, Iowa State University, Ames, Iowa, United States of America
| | - M. Carmen Valero
- Department of Entomology, University of Illinois, Urbana-Champaign, Illinois, United States of America
| | - Weilin Sun
- Department of Entomology, University of Illinois, Urbana-Champaign, Illinois, United States of America
| | - Keon Mook Seong
- Department of Entomology, University of Illinois, Urbana-Champaign, Illinois, United States of America
| | - William M. Muir
- Department of Animal Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - John M. Clark
- Department of Veterinary & Animal Science, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Barry R. Pittendrigh
- Department of Entomology, University of Illinois, Urbana-Champaign, Illinois, United States of America
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22
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Mecklenburg KL, Freed SA, Raval M, Quintero OA, Yengo CM, O'Tousa JE. Invertebrate and vertebrate class III myosins interact with MORN repeat-containing adaptor proteins. PLoS One 2015; 10:e0122502. [PMID: 25822849 PMCID: PMC4379085 DOI: 10.1371/journal.pone.0122502] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 02/18/2015] [Indexed: 12/22/2022] Open
Abstract
In Drosophila photoreceptors, the NINAC-encoded myosin III is found in a complex with a small, MORN-repeat containing, protein Retinophilin (RTP). Expression of these two proteins in other cell types showed NINAC myosin III behavior is altered by RTP. NINAC deletion constructs were used to map the RTP binding site within the proximal tail domain of NINAC. In vertebrates, the RTP ortholog is MORN4. Co-precipitation experiments demonstrated that human MORN4 binds to human myosin IIIA (MYO3A). In COS7 cells, MORN4 and MYO3A, but not MORN4 and MYO3B, co-localize to actin rich filopodia extensions. Deletion analysis mapped the MORN4 binding to the proximal region of the MYO3A tail domain. MYO3A dependent MORN4 tip localization suggests that MYO3A functions as a motor that transports MORN4 to the filopodia tips and MORN4 may enhance MYO3A tip localization by tethering it to the plasma membrane at the protrusion tips. These results establish conserved features of the RTP/MORN4 family: they bind within the tail domain of myosin IIIs to control their behavior.
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Affiliation(s)
- Kirk L. Mecklenburg
- Department of Biology, Indiana University South Bend, South Bend, Indiana, United States of America
| | - Stephanie A. Freed
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Manmeet Raval
- Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania, United States of America
| | - Omar A. Quintero
- Department of Biology, University of Richmond, Richmond, Virginia, United States of America
| | - Christopher M. Yengo
- Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania, United States of America
- * E-mail: (CY); (JO)
| | - Joseph. E. O'Tousa
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
- * E-mail: (CY); (JO)
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23
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An BC, Sakai T, Komaba S, Kishi H, Kobayashi S, Kim JY, Ikebe R, Ikebe M. Phosphorylation of the kinase domain regulates autophosphorylation of myosin IIIA and its translocation in microvilli. Biochemistry 2014; 53:7835-45. [PMID: 25402663 PMCID: PMC4270376 DOI: 10.1021/bi501247z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
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Motor activity of myosin III is regulated
by autophosphorylation.
To investigate the role of the kinase activity on the transporter
function of myosin IIIA (Myo3A), we identified the phosphorylation
sites of kinase domain (KD), which is responsible for the regulation
of kinase activity and thus motor function. Using mass spectrometry,
we identified six phosphorylation sites in the KD, which are highly
conserved among class III myosins and Ste20-related misshapen (Msn)
kinases. Two predominant sites, Thr184 and Thr188, in KD are important for phosphorylation of the KD as well as the
motor domain, which regulates the affinity for actin. In the Caco2
cells, the full-length human Myo3A (hMyo3AFull) markedly enlarged
the microvilli, although it did not show discrete localization within
the microvilli. On the other hand, hMyo3AFull(T184A) and hMyo3AFull(T188A)
both showed clear localization at the microvilli tips. Our results
suggest that Myo3A induces large actin bundle formation to form microvilli,
and phosphorylation of KD at Thr184 and Thr188 is critical for the kinase activity of Myo3A, and regulation of
Myo3A translocation to the tip of microvilli. Retinal extracts potently
dephosphorylate both KD and motor domain without IQ motifs (MDIQo),
which was inhibited by okadaic acid (OA) with nanomolar range and
by tautomycetin (TMC) with micromolar range. The results suggest that
Myo3A phosphatase is protein phosphatase type 2A (PP2A). Supporting
this result, recombinant PP2Ac potently dephosphorylates both KD and
MDIQo. We propose that the phosphorylation–dephosphorylation
mechanism plays an essential role in mediating the transport and actin
bundle formation and stability functions of hMyo3A.
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Affiliation(s)
- Byung Chull An
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School , Worcester, Massachusetts 01605, United States
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24
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Batters C, Veigel C, Homsher E, Sellers JR. To understand muscle you must take it apart. Front Physiol 2014; 5:90. [PMID: 24653704 PMCID: PMC3949407 DOI: 10.3389/fphys.2014.00090] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 02/16/2014] [Indexed: 01/08/2023] Open
Abstract
Striated muscle is an elegant system for study at many levels. Much has been learned about the mechanism of contraction from studying the mechanical properties of intact and permeabilized (or skinned) muscle fibers. Structural studies using electron microscopy, X-ray diffraction or spectroscopic probes attached to various contractile proteins were possible because of the highly ordered sarcomeric arrangement of actin and myosin. However, to understand the mechanism of force generation at a molecular level, it is necessary to take the system apart and study the interaction of myosin with actin using in vitro assays. This reductionist approach has lead to many fundamental insights into how myosin powers muscle contraction. In addition, nature has provided scientists with an array of muscles with different mechanical properties and with a superfamily of myosin molecules. Taking advantage of this diversity in myosin structure and function has lead to additional insights into common properties of force generation. This review will highlight the development of the major assays and methods that have allowed this combined reductionist and comparative approach to be so fruitful. This review highlights the history of biochemical and biophysical studies of myosin and demonstrates how a broad comparative approach combined with reductionist studies have led to a detailed understanding of how myosin interacts with actin and uses chemical energy to generate force and movement in muscle contraction and motility in general.
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Affiliation(s)
- Christopher Batters
- Department of Cellular Physiology and Centre for Nanosciences (CeNS), Ludwig-Maximilians-Universität München München, Germany
| | - Claudia Veigel
- Department of Cellular Physiology and Centre for Nanosciences (CeNS), Ludwig-Maximilians-Universität München München, Germany
| | - Earl Homsher
- Physiology Department, University of California Los Angeles Los Angeles, CA, USA
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
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Quintero OA, Unrath WC, Stevens SM, Manor U, Kachar B, Yengo CM. Myosin 3A kinase activity is regulated by phosphorylation of the kinase domain activation loop. J Biol Chem 2013; 288:37126-37. [PMID: 24214986 DOI: 10.1074/jbc.m113.511014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Class III myosins are unique members of the myosin superfamily in that they contain both a motor and kinase domain. We have found that motor activity is decreased by autophosphorylation, although little is known about the regulation of the kinase domain. We demonstrate by mass spectrometry that Thr-178 and Thr-184 in the kinase domain activation loop and two threonines in the loop 2 region of the motor domain are autophosphorylated (Thr-908 and Thr-919). The kinase activity of MYO3A 2IQ with the phosphomimic (T184E) or phosphoblock (T184A) mutations demonstrates that kinase activity is reduced 30-fold as a result of the T184A mutation, although the Thr-178 site only had a minor impact on kinase activity. Interestingly, the actin-activated ATPase activity of MYO3A 2IQ is slightly reduced as a result of the T178A and T184A mutations suggesting coupling between motor and kinase domains. Full-length GFP-tagged T184A and T184E MYO3A constructs transfected into COS7 cells do not disrupt the ability of MYO3A to localize to filopodia structures. In addition, we demonstrate that T184E MYO3A reduces filopodia elongation in the presence of espin-1, whereas T184A enhances filopodia elongation in a similar fashion to kinase-dead MYO3A. Our results suggest that as MYO3A accumulates at the tips of actin protrusions, autophosphorylation of Thr-184 enhances kinase activity resulting in phosphorylation of the MYO3A motor and reducing motor activity. The differential regulation of the kinase and motor activities allows for MYO3A to precisely self-regulate its concentration in the actin bundle-based structures of cells.
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Affiliation(s)
- Omar A Quintero
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033
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26
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Chu B, Liu CH, Sengupta S, Gupta A, Raghu P, Hardie RC. Common mechanisms regulating dark noise and quantum bump amplification in Drosophila photoreceptors. J Neurophysiol 2013; 109:2044-55. [PMID: 23365183 DOI: 10.1152/jn.00001.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Absolute visual thresholds are limited by "dark noise," which in Drosophila photoreceptors is dominated by brief (∼10 ms), small (∼2 pA) inward current events, occurring at ∼2/s, believed to reflect spontaneous G protein activations. These dark events were increased in rate and amplitude by a point mutation in myosin III (NINAC), which disrupts its interaction with the scaffolding protein, INAD. This phenotype mimics that previously described in null mutants of ninaC (no inactivation no afterpotential; encoding myosin III) and an associated protein, retinophilin (rtp). Dark noise was similarly increased in heterozygote mutants of diacylglycerol kinase (rdgA/+). Dark noise in ninaC, rtp, and rdgA/+ mutants was greatly suppressed by mutations of the Gq α-subunit (Gαq) and the major light-sensitive channel (trp) but not rhodopsin. ninaC, rtp, and rdgA/+ mutations also all facilitated residual light responses in Gαq and PLC hypomorphs. Raising cytosolic Ca(2+) in the submicromolar range increased dark noise, facilitated activation of transient receptor potential (TRP) channels by exogenous agonist, and again facilitated light responses in Gαq hypomorphs. Our results indicate that RTP, NINAC, INAD, and diacylglycerol kinase, together with a Ca(2+)-dependent threshold, share common roles in suppressing dark noise and regulating quantum bump generation; consequently, most spontaneous G protein activations fail to generate dark events under normal conditions. By contrast, quantum bump generation is reliable but delayed until sufficient G proteins and PLC are activated to overcome threshold, thereby ensuring generation of full-size bumps with high quantum efficiency.
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Affiliation(s)
- Brian Chu
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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27
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Lee J. Drosophila mosaic screen identifies diehard mutants as norpA P24 suppressors. Genes Genomics 2012. [DOI: 10.1007/s13258-012-0097-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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28
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Regulation of arrestin translocation by Ca2+ and myosin III in Drosophila photoreceptors. J Neurosci 2012; 32:9205-16. [PMID: 22764229 DOI: 10.1523/jneurosci.0924-12.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Upon illumination several phototransduction proteins translocate between cell body and photosensory compartments. In Drosophila photoreceptors arrestin (Arr2) translocates from cell body to the microvillar rhabdomere down a diffusion gradient created by binding of Arr2 to photo-isomerized metarhodopsin. Translocation is profoundly slowed in mutants of key phototransduction proteins including phospholipase C (PLC) and the Ca(2+)-permeable transient receptor potential channel (TRP), but how the phototransduction cascade accelerates Arr2 translocation is unknown. Using real-time fluorescent imaging of Arr2-green fluorescent protein translocation in dissociated ommatidia, we show that translocation is profoundly slowed in Ca(2+)-free solutions. Conversely, in a blind PLC mutant with ∼100-fold slower translocation, rapid translocation was rescued by the Ca(2+) ionophore, ionomycin. In mutants lacking NINAC (calmodulin [CaM] binding myosin III) in the cell body, translocation remained rapid even in Ca(2+)-free solutions. Immunolabeling revealed that Arr2 in the cell body colocalized with NINAC in the dark. In intact eyes, the impaired translocation found in trp mutants was rescued in ninaC;trp double mutants. Nevertheless, translocation following prolonged dark adaptation was significantly slower in ninaC mutants, than in wild type: a difference that was reflected in the slow decay of the electroretinogram. The results suggest that cytosolic NINAC is a Ca(2+)-dependent binding target for Arr2, which protects Arr2 from immobilization by a second potential sink that sequesters and releases arrestin on a much slower timescale. We propose that rapid Ca(2+)/CaM-dependent release of Arr2 from NINAC upon Ca(2+) influx accounts for the acceleration of translocation by phototransduction.
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Montell C. Drosophila visual transduction. Trends Neurosci 2012; 35:356-63. [PMID: 22498302 DOI: 10.1016/j.tins.2012.03.004] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 03/06/2012] [Accepted: 03/11/2012] [Indexed: 11/26/2022]
Abstract
Visual transduction in the Drosophila compound eye functions through a pathway that couples rhodopsin to phospholipase C (PLC) and the opening of transient receptor potential (TRP) channels. This cascade differs from phototransduction in mammalian rods and cones, but is remarkably similar to signaling in mammalian intrinsically photosensitive retinal ganglion cells (ipRGCs). In this review, I focus on recent advances in the fly visual system, including the discovery of a visual cycle and insights into the machinery and mechanisms involved in generating a light response in photoreceptor cells.
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Affiliation(s)
- Craig Montell
- Departments of Biological Chemistry and Neuroscience, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Pak WL, Shino S, Leung HT. PDA (prolonged depolarizing afterpotential)-defective mutants: the story of nina's and ina's--pinta and santa maria, too. J Neurogenet 2012; 26:216-37. [PMID: 22283778 PMCID: PMC3433705 DOI: 10.3109/01677063.2011.642430] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Our objective is to present a comprehensive view of the PDA (prolonged depolarizing afterpotential)-defective Drosophila mutants, nina's and ina's, from the discussion of the PDA and the PDA-based mutant screening strategy to summaries of the knowledge gained through the studies of mutants generated using the strategy. The PDA is a component of the light-evoked photoreceptor potential that is generated when a substantial fraction of rhodopsin is photoconverted to its active form, metarhodopsin. The PDA-based mutant screening strategy was adopted to enhance the efficiency and efficacy of ERG (electroretinogram)-based screening for identifying phototransduction-defective mutants. Using this strategy, two classes of PDA-defective mutants were identified and isolated, nina and ina, each comprising multiple complementation groups. The nina mutants are characterized by allele-dependent reduction in the major rhodopsin, Rh1, whereas the ina mutants display defects in some aspects of functions related to the transduction channel, TRP (transient receptor potential). The signaling proteins that have been identified and elucidated through the studies of nina mutants include the Drosophila opsin protein (NINAE), the chaperone protein for nascent opsin (NINAA), and the multifunctional protein, NINAC, required in multiple steps of the Drosophila phototransduction cascade. Also identified by the nina mutants are some of the key enzymes involved in the biogenesis of the rhodopsin chromophore. As for the ina mutants, they led to the discovery of the scaffold protein, INAD, responsible for the nucleation of the supramolecular signaling complex. Also identified by the ina mutants is one of the key members of the signaling complex, INAC (ePKC), and two other proteins that are likely to be important, though their roles in the signaling cascade have not yet been fully elucidated. In most of these cases, the protein identified is the first member of its class to be so recognized.
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Affiliation(s)
- William L Pak
- Department of Biological Sciences, Purdue University, 915 W. State Street, West Lafayette, IN 47907-2054, USA.
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Pak WL, Leung HT. Genetic Approaches to Visual Transduction in Drosophila melanogaster. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308242] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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32
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Hardie RC. Phototransduction mechanisms in Drosophila microvillar photoreceptors. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/wmts.20] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Dalal JS, Stevens SM, Alvarez S, Munoz N, Kempler KE, Dosé AC, Burnside B, Battelle BA. Mouse class III myosins: kinase activity and phosphorylation sites. J Neurochem 2011; 119:772-84. [PMID: 21895655 DOI: 10.1111/j.1471-4159.2011.07468.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As class III unconventional myosins are motor proteins with an N-terminal kinase domain, it seems likely they play a role in both signaling and actin based transport. A growing body of evidence indicates that the motor functions of human class IIIA myosin, which has been implicated in progressive hearing loss, are modulated by intermolecular autophosphorylation. However, the phosphorylation sites have not been identified. We studied the kinase activity and phosphorylation sites of mouse class III myosins, mMyo3A and 3B, which are highly similar to their human orthologs. We demonstrate that the kinase domains of mMyo3A and 3B are active kinases, and that they have similar, if not identical, substrate specificities. We show that the kinase domains of these proteins autophosphorylate, and that they can phosphorylate sites within their myosin and tail domains. Using liquid chromatography-mass spectrometry, we identified phosphorylated sites in the kinase, myosin motor and tail domains of both mMyo3A and 3B. Most of the phosphorylated sites we identified and their consensus phosphorylation motifs are highly conserved among vertebrate class III myosins, including human class III myosins. Our findings are a major step toward understanding how the functions of class III myosins are regulated by phosphorylation.
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Affiliation(s)
- Jasbir S Dalal
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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Abstract
This review recounts the early history of Drosophila phototransduction genetics, covering the period between approximately 1966 to 1979. Early in this period, the author felt that there was an urgent need for a new approach in phototransduction research. Through inputs from a number of colleagues, he was led to consider isolating Drosophila mutants that are defective in the electroretinogram. Thanks to the efforts of dedicated associates and technical staff, by the end of this period, he was able to accumulate a large number of such mutants. Particularly important in this effort was the use of the mutant assay protocol based on the "prolonged depolarizing afterpotential." This collection of mutants formed the basis of the subsequent intensive investigations of the Drosophila phototransduction cascade by many investigators.
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Affiliation(s)
- William L Pak
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2054, USA.
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Walsh VL, Raviv D, Dror AA, Shahin H, Walsh T, Kanaan MN, Avraham KB, King MC. A mouse model for human hearing loss DFNB30 due to loss of function of myosin IIIA. Mamm Genome 2010; 22:170-7. [PMID: 21165622 DOI: 10.1007/s00335-010-9310-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Accepted: 11/16/2010] [Indexed: 10/18/2022]
Abstract
The motor protein myosin IIIA is critical for maintenance of normal hearing. Homozygosity and compound heterozygosity for loss-of-function mutations in MYO3A, which encodes myosin IIIA, are responsible for inherited human progressive hearing loss DFNB30. To further evaluate this hearing loss, we constructed a mouse model, Myo3a(KI/KI), that harbors the mutation equivalent to the nonsense allele responsible for the most severe human phenotype. Myo3a(KI/KI) mice were compared to their wild-type littermates. Myosin IIIA, with a unique N-terminal kinase domain and a C-terminal actin-binding domain, localizes to the tips of stereocilia in wild-type mice but is absent in the mutant. The phenotype of the Myo3a(KI/KI) mouse parallels the phenotype of human DFNB30. Hearing loss, as measured by auditory brainstem response, is reduced and progresses significantly with age. Vestibular function is normal. Outer hair cells of Myo3a(KI/KI) mice degenerate with age in a pattern consistent with their progressive hearing loss.
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Affiliation(s)
- Vanessa L Walsh
- Department of Medicine, University of Washington, Seattle, WA 98195-7720, USA
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Dependence on a retinophilin/myosin complex for stability of PKC and INAD and termination of phototransduction. J Neurosci 2010; 30:11337-45. [PMID: 20739554 DOI: 10.1523/jneurosci.2709-10.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Normal termination of signaling is essential to reset signaling cascades, especially those such as phototransduction that are turned on and off with great rapidity. Genetic approaches in Drosophila led to the identification of several proteins required for termination, including protein kinase C (PKC), NINAC (neither inactivation nor afterpotential C) p174, which consists of fused protein kinase and myosin domains, and a PDZ (postsynaptic density-95/Discs Large/zona occludens-1) scaffold protein, INAD (inactivation no afterpotential D). Here, we describe a mutation affecting a poorly characterized but evolutionarily conserved protein, Retinophilin (Retin), which is expressed primarily in the phototransducing compartment of photoreceptor cells, the rhabdomeres. Retin and NINAC formed a complex and were mutually dependent on each other for expression. Loss of retin resulted in an age-dependent impairment in termination of phototransduction. Mutations that affect termination of the photoresponse typically lead to a reduction in levels of the major rhodopsin (Rh1) to attenuate signaling. Consistent with the slower termination in retin(1), the mutant photoreceptor cells exhibited increased endocytosis of Rh1 and a decline in Rh1 protein. The slower termination in retin(1) was a consequence of a cascade of defects, which began with the reduction in NINAC p174 levels. The diminished p174 concentration caused a decrease in INAD. Because PKC requires interaction with INAD for protein stability, this leads to reduction in PKC levels. The decline in PKC was age dependent and paralleled the onset of the termination phenotype in retin(1) mutant flies. We conclude that the slower termination of the photoresponse in retin(1) resulted from a requirement for the Retin/NINAC complex for stability of INAD and PKC.
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Quintero OA, Moore JE, Unrath WC, Manor U, Salles FT, Grati M, Kachar B, Yengo CM. Intermolecular autophosphorylation regulates myosin IIIa activity and localization in parallel actin bundles. J Biol Chem 2010; 285:35770-82. [PMID: 20826793 DOI: 10.1074/jbc.m110.144360] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Myosin IIIa (Myo3A) transports cargo to the distal end of actin protrusions and contains a kinase domain that is thought to autoregulate its activity. Because Myo3A tends to cluster at the tips of actin protrusions, we investigated whether intermolecular phosphorylation could regulate Myo3A biochemical activity, cellular localization, and cellular function. Inactivation of Myo3A 2IQ kinase domain with the point mutation K50R did not alter maximal ATPase activity, whereas phosphorylation of Myo3A 2IQ resulted in reduced maximal ATPase activity and actin affinity. The rate and degree of Myo3A 2IQ autophosphorylation was unchanged by the presence of actin but was found to be dependent upon Myo3A 2IQ concentration within the range of 0.1 to 1.2 μm, indicating intermolecular autophosphorylation. In cultured cells, we observed that the filopodial tip localization of Myo3A lacking the kinase domain decreased when co-expressed with kinase-active, full-length Myo3A. The cellular consequence of reduced Myo3A tip localization was decreased filopodial density along the cell periphery, identifying a novel cellular function for Myo3A in mediating the formation and stability of actin-based protrusions. Our results suggest that Myo3A motor activity is regulated through a mechanism involving concentration-dependent autophosphorylation. We suggest that this regulatory mechanism plays an essential role in mediating the transport and actin bundle formation/stability functions of Myo3A.
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Affiliation(s)
- Omar A Quintero
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033, USA
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Komaba S, Watanabe S, Umeki N, Sato O, Ikebe M. Effect of phosphorylation in the motor domain of human myosin IIIA on its ATP hydrolysis cycle. Biochemistry 2010; 49:3695-702. [PMID: 20192276 DOI: 10.1021/bi902211w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous findings suggested that the motor activity of human myosin IIIA (HM3A) is influenced by phosphorylation [Kambara, T., et al. (2006) J. Biol. Chem. 281, 37291-37301]; however, how phosphorylation controls the motor activity of HM3A is obscure. In this study, we clarify the kinetic basis of the effect of phosphorylation on the ATP hydrolysis cycle of the motor domain of HM3A (huM3AMD). The affinity of human myosin IIIA for filamentous actin in the presence of ATP is more than 100-fold decreased by phosphorylation, while the maximum rate of ATP turnover is virtually unchanged. The rate of release of ADP from acto-phosphorylated huM3AMD is 6-fold greater than the overall cycle rate, and thus not a rate-determining step. The rate constant of the ATP hydrolysis step of the actin-dissociated form is markedly increased by phosphorylation by 30-fold. The dissociation constant for dissociation of the ATP-bound form of huM3AMD from actin is greatly increased by phosphorylation, and this result agrees well with the significant increase in the K(actin) value of the steady-state ATPase reaction. The rate constant of the P(i) off step is greater than 60 s(-1), suggesting that this step does not limit the overall ATP hydrolysis cycle rate. Our kinetic model indicates that phosphorylation induces the dissociation of huM3AMD from actin during the ATP hydrolysis cycle, and this is due to the phosphorylation-dependent marked decrease in the affinity of huM3AMD.ATP for actin and the increase in the ATP hydrolysis rate of huM3AMD in the actin-dissociated state. These results suggest that the phosphorylation of myosin IIIA significantly lowers the duty ratio, which may influence the cargo transporting ability of the native form of myosin IIIA that contains the ATP-independent actin binding site in the tail.
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Affiliation(s)
- Shigeru Komaba
- Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01655-0127, USA
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Sanxaridis PD, Tsunoda S. A forward genetic screen in Drosophila melanogaster to identify mutations affecting INAD localization in photoreceptor cells. Fly (Austin) 2010; 4:95-103. [PMID: 20404479 DOI: 10.4161/fly.4.2.11861] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In Drosophila photoreceptors, the multivalent PDZ protein INAD interacts with multiple signaling components and localizes complexes to the rhabdomere, a subcellular compartment specialized for phototransduction. Since this localization is critical for signaling, we conducted a genetic screen of the third chromosome for mutations that result in mislocalization of an INAD-GFP fusion protein. We identified seven mutant lines that fall into two complementation groups, idl (INAD localization)-A and idl-B. We show that idl-A mutants fail to complement with chaoptic (chp) mutants. Since chaoptin is a structural component of the rhabdomere, mislocalization of INAD may be a secondary effect of the retinal degeneration in chp and idl-A mutants. Genetic complementation and DNA sequencing reveal that the two idl-B mutants represent new alleles of trp, a gene encoding the major light-activated channel. The molecular change in each allele affects a highly conserved residue in either an ankyrin domain on the N-terminus or in the S6 transmembrane domain of TRP. These changes lead to the loss of TRP protein. TRP has previously been shown to anchor INAD in the rhabdomeres, therefore the independent identification of two trp alleles validates our screen for INAD-GFP localization. One possibility is that a limited number of proteins are required for localizing INAD-signaling complexes. A similar screen of the X and second chromosomes may be required to find the remaining players involved.
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Zuniga FI, Ochoa GH, Kelly SD, Robles LJ. S-crystallin and arginine kinase bind F-actin in light- and dark-adapted octopus retinas. Curr Eye Res 2009; 28:343-50. [PMID: 15287371 DOI: 10.1076/ceyr.28.5.343.28683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
PURPOSE Rhabdomere microvilli dramatically reorganize in conditions of light and dark. This reorganization involves remodeling of the microvillus actin cytoskeleton. We are using the rhabdomeric retina of Octopus bimaculoides to identify actin-binding proteins that may be involved in this remodeling. METHODS Octopus were light-/dark-adapted, retinas separated into dorsal and ventral halves, and homogenized. Actin-binding proteins were recognized using F-actin overlay blot assays and selected proteins from the overlays were identified using N-terminal sequencing methods or mass spectroscopy. Protein concentrations were quantified and compared by statistical analysis. RESULTS Total protein gels of light-/dark-adapted, ventral/dorsal halves were almost identical except for a protein band at 26 kD. The relative amount of this protein in the dark was almost double that found in the light. The levels of other proteins did not vary significantly between the light and dark. F-actin overlays also showed matching patterns of actin-binding proteins except for the 26 kD protein. Although the 26 kD protein from light-adapted retinas transferred to the blotting membranes, it did not bind F-actin while the 26 kD protein on overlays from dark-adapted retinas always demonstrated F-actin binding. Besides the 26 kD protein, other proteins at 200 kD, 80 kD, 40 kD appeared on the overlays. These proteins and the 26 kD protein were sequenced and identified as hemocynanin, transitional ER ATPase, arginine kinase and S-crystallin, respectively. CONCLUSIONS The amount of S-crystallin present in the octopus retina is significantly greater in dark-adapted retinas and it binds to F-actin. In the light, the level of S-crystallin is greatly reduced and there is no apparent F-actin binding. No other studies, to our knowledge, show that S-crystallin binds to the actin cytoskeleton or that its expression is regulated by light. Arginine kinase may provide energy for cytoskeletal remodeling as it may in other neural tissues.
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Affiliation(s)
- Freddi Isaac Zuniga
- Department of Chemistry, California State University, Dominguez Hills, Carson, CA, USA
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Katti C, Dalal JS, Dosé AC, Burnside B, Battelle BA. Cloning and distribution of myosin 3B in the mouse retina: differential distribution in cone outer segments. Exp Eye Res 2009; 89:224-37. [PMID: 19332056 DOI: 10.1016/j.exer.2009.03.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 03/17/2009] [Accepted: 03/18/2009] [Indexed: 11/30/2022]
Abstract
Class III myosins are important for the function and survival of photoreceptors and ciliary hair cells. Although vertebrates possess two class III myosin genes, myo3A and myo3B, recent studies have focused on Myo3A because mutations in the human gene are implicated in progressive hearing loss. Myo3B may compensate for defects in Myo3A, yet little is known about its distribution and function. This study focuses on Myo3B expression in the mouse retina. We cloned two variants of myo3B from mouse retina and determined that they are expressed early in retinal development. In this study we show for the first time in a mammal that both Myo3B and Myo3A proteins are present in inner segments of all photoreceptors. Myo3B is also present in outer segments of S opsin-immunoreactive cones but not M opsin dominant cones. Myo3B is also detected in rare cells of the inner nuclear layer and some ganglion cells. Myo3B may have diverse roles in retinal neurons. In photoreceptor inner segments Myo3B is positioned appropriately to prevent photoreceptor loss of function caused by Myo3A defects.
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Affiliation(s)
- Christiana Katti
- Department of Neuroscience and Whitney Laboratory for Marine Bioscience, University of Florida, St Augustine, FL 32080, USA
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Lin-Jones J, Sohlberg L, Dosé A, Breckler J, Hillman DW, Burnside B. Identification and localization of myosin superfamily members in fish retina and retinal pigmented epithelium. J Comp Neurol 2009; 513:209-23. [PMID: 19137585 PMCID: PMC2785712 DOI: 10.1002/cne.21958] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Myosins are cytoskeletal motors critical for generating the forces necessary for establishing cell structure and mediating actin-dependent cell motility. In each cell type a multitude of myosins are expressed, each myosin contributing to aspects of morphogenesis, transport, or motility occurring in that cell type. To examine the roles of myosins in individual retinal cell types, we first used polymerase chain reaction (PCR) screening to identify myosins expressed in retina and retinal pigmented epithelium (RPE), followed by immunohistochemistry to examine the cellular and subcellular localizations of seven of these expressed myosins. In the myosin PCR screen of cDNA from striped bass retina and striped bass RPE, we amplified 17 distinct myosins from eight myosin classes from retinal cDNA and 11 distinct myosins from seven myosin classes from RPE cDNA. By using antibodies specific for myosins IIA, IIB, IIIA, IIIB, VI, VIIA, and IXB, we examined the localization patterns of these myosins in retinas and RPE of fish, and in isolated inner/outer segment fragments of green sunfish photoreceptors. Each of the myosins exhibited unique expression patterns in fish retina. Individual cell types expressed multiple myosin family members, some of which colocalized within a particular cell type. Because much is known about the functions and properties of these myosins from studies in other systems, their cellular and subcellular localization patterns in the retina help us understand which roles they might play in the vertebrate retina and RPE.
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Affiliation(s)
- Jennifer Lin-Jones
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA.
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Liu CH, Satoh AK, Postma M, Huang J, Ready DF, Hardie RC. Ca2+-dependent metarhodopsin inactivation mediated by calmodulin and NINAC myosin III. Neuron 2008; 59:778-89. [PMID: 18786361 DOI: 10.1016/j.neuron.2008.07.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 06/03/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
Abstract
Phototransduction in flies is the fastest known G protein-coupled signaling cascade, but how this performance is achieved remains unclear. Here, we investigate the mechanism and role of rhodopsin inactivation. We determined the lifetime of activated rhodopsin (metarhodopsin = M( *)) in whole-cell recordings from Drosophila photoreceptors by measuring the time window within which inactivating M( *) by photoreisomerization to rhodopsin could suppress responses to prior illumination. M( *) was inactivated rapidly (tau approximately 20 ms) under control conditions, but approximately 10-fold more slowly in Ca2+-free solutions. This pronounced Ca2+ dependence of M( *) inactivation was unaffected by mutations affecting phosphorylation of rhodopsin or arrestin but was abolished in mutants of calmodulin (CaM) or the CaM-binding myosin III, NINAC. This suggests a mechanism whereby Ca2+ influx acting via CaM and NINAC accelerates the binding of arrestin to M( *). Our results indicate that this strategy promotes quantum efficiency, temporal resolution, and fidelity of visual signaling.
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Affiliation(s)
- Che-Hsiung Liu
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge CB23DY, UK
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Wang T, Wang X, Xie Q, Montell C. The SOCS box protein STOPS is required for phototransduction through its effects on phospholipase C. Neuron 2008; 57:56-68. [PMID: 18184564 DOI: 10.1016/j.neuron.2007.11.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Revised: 09/14/2007] [Accepted: 11/08/2007] [Indexed: 10/22/2022]
Abstract
Phosphoinositide-specific phospholipase C (PLC) isozymes play roles in a diversity of processes including Drosophila phototransduction. In fly photoreceptor cells, the PLCbeta encoded by norpA is critical for activation of TRP channels. Here, we describe a PLCbeta regulator, STOPS, which encodes a SOCS box protein. Mutation of stops resulted in a reduced concentration of NORPA and a defect in stopping signaling following cessation of the light stimulus. NORPA has been proposed to have dual roles as a PLC- and GTPase-activating protein (GAP). We found that the slow termination resulting from expressing low levels of wild-type NORPA was suppressed by addition of normal amounts of an altered NORPA, which had wild-type GAP activity, but no PLC activity. STOPS is the first protein identified that specifically regulates PLCbeta protein concentration. Moreover, this work demonstrates that a PLCbeta derivative that does not promote TRP channel activation, still contributes to signaling in vivo.
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Affiliation(s)
- Tao Wang
- Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Abstract
Drosophila visual signaling, a G-protein-coupled phospholipase Cbeta (PLCbeta)-mediated mechanism, is regulated by eye-protein kinase C (PKC) that promotes light adaptation and fast deactivation, most likely via phosphorylation of inactivation no afterpotential D (INAD) and TRP (transient receptor potential). To reveal the critical phosphatases that dephosphorylate INAD, we used several biochemical analyses and identified protein phosphatase 2A (PP2A) as a candidate. Importantly, the catalytic subunit of PP2A, microtubule star (MTS), is copurified with INAD, and an elevated phosphorylation of INAD by eye-PKC was observed in three mts heterozygotes. To explore whether PP2A (MTS) regulates dephosphorylation of INAD by counteracting eye-PKC [INAC (inactivation no afterpotential C] in vivo, we performed ERG recordings. We discovered that inaC(P209) was semidominant, because inaC(P209) heterozygotes displayed abnormal light adaptation and slow deactivation. Interestingly, the deactivation defect of inaC(P209) heterozygotes was rescued by the mts(XE2258) heterozygous background. In contrast, mts(XE2258) failed to modify the severe deactivation of norpA(P16), indicating that MTS does not modulate NORPA (no receptor potential A) (PLCbeta). Together, our results strongly indicate that dephosphorylation of INAD is catalyzed by PP2A, and a reduction of PP2A can compensate for a partial loss of function in eye-PKC, restoring the fast deactivation kinetics in vivo. We thus propose that the fast deactivation of the visual response is modulated in part by the phosphorylation of INAD.
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Frechter S, Elia N, Tzarfaty V, Selinger Z, Minke B. Translocation of Gq alpha mediates long-term adaptation in Drosophila photoreceptors. J Neurosci 2007; 27:5571-83. [PMID: 17522302 PMCID: PMC1934929 DOI: 10.1523/jneurosci.0310-07.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Light adaptation is a process that enables photoreceptor cells to operate over a wide range of light intensities without saturation. In invertebrate photoreceptors, fast adaptation is mediated by a Ca2+-dependent negative-feedback mechanism, which mainly affects the terminal steps of the cascade. Therefore, the response to each photon is smaller as light intensity increases, accommodating both high sensitivity and a vast dynamic range. Here, we describe a novel type of adaptation, which is mediated by one of the first steps in the phototransduction cascade affecting the sensitivity to absorbed photons. Long exposure to light resulted in dramatic reduction in the probability of each absorbed photon to elicit a response, whereas the size and shape of each single photon response did not change. To dissect the molecular mechanism underlying this form of adaptation we used a series of Drosophila mutants. Genetic dissection showed a pivotal role for light-induced translocation of Gq alpha between the signaling membrane and the cytosol. Biochemical studies revealed that the sensitivity to light depends on membrane Gq alpha concentration, which was modulated either by light or by mutations that impaired its targeting to the membrane. We conclude that long-term adaptation is mediated by the movement of Gq alpha from the signaling membrane to the cytosol, thereby reducing the probability of each photon to elicit a response. The slow time scale of this adaptation fits well with day/night light intensity changes, because there is no need to maintain single photon sensitivity during daytime.
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Affiliation(s)
| | - Natalie Elia
- Biological Chemistry and Kühne Minerva Center for Studies of Visual Transduction, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | | | - Zvi Selinger
- Biological Chemistry and Kühne Minerva Center for Studies of Visual Transduction, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
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Wang T, Jiao Y, Montell C. Dissection of the pathway required for generation of vitamin A and for Drosophila phototransduction. ACTA ACUST UNITED AC 2007; 177:305-16. [PMID: 17452532 PMCID: PMC2064138 DOI: 10.1083/jcb.200610081] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Dietary carotenoids are precursors for the production of retinoids, which participate in many essential processes, including the formation of the photopigment rhodopsin. Despite the importance of conversion of carotenoids to vitamin A (all-trans-retinol), many questions remain concerning the mechanisms that promote this process, including the uptake of carotenoids. We use the Drosophila visual system as a genetic model to study retinoid formation from β-carotene. In a screen for mutations that affect the biosynthesis of rhodopsin, we identified a class B scavenger receptor, SANTA MARIA. We demonstrate that SANTA MARIA functions upstream of vitamin A formation in neurons and glia, which are outside of the retina. The protein is coexpressed and functionally coupled with the β, β-carotene-15, 15′-monooxygenase, NINAB, which converts β-carotene to all-trans-retinal. Another class B scavenger receptor, NINAD, functions upstream of SANTA MARIA in the uptake of carotenoids, enabling us to propose a pathway involving multiple extraretinal cell types and proteins essential for the formation of rhodopsin.
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Affiliation(s)
- Tao Wang
- Department of Biological Chemistry, Department of Neuroscience, and Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Wang T, Montell C. Phototransduction and retinal degeneration in Drosophila. Pflugers Arch 2007; 454:821-47. [PMID: 17487503 DOI: 10.1007/s00424-007-0251-1] [Citation(s) in RCA: 215] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 03/05/2007] [Indexed: 01/05/2023]
Abstract
Drosophila visual transduction is the fastest known G-protein-coupled signaling cascade and has therefore served as a genetically tractable animal model for characterizing rapid responses to sensory stimulation. Mutations in over 30 genes have been identified, which affect activation, adaptation, or termination of the photoresponse. Based on analyses of these genes, a model for phototransduction has emerged, which involves phosphoinoside signaling and culminates with opening of the TRP and TRPL cation channels. Many of the proteins that function in phototransduction are coupled to the PDZ containing scaffold protein INAD and form a supramolecular signaling complex, the signalplex. Arrestin, TRPL, and G alpha(q) undergo dynamic light-dependent trafficking, and these movements function in long-term adaptation. Other proteins play important roles either in the formation or maturation of rhodopsin, or in regeneration of phosphatidylinositol 4,5-bisphosphate (PIP2), which is required for the photoresponse. Mutation of nearly any gene that functions in the photoresponse results in retinal degeneration. The underlying bases of photoreceptor cell death are diverse and involve mechanisms such as excessive endocytosis of rhodopsin due to stable rhodopsin/arrestin complexes and abnormally low or high levels of Ca2+. Drosophila visual transduction appears to have particular relevance to the cascade in the intrinsically photosensitive retinal ganglion cells in mammals, as the photoresponse in these latter cells appears to operate through a remarkably similar mechanism.
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Affiliation(s)
- Tao Wang
- Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Kempler K, Tóth J, Yamashita R, Mapel G, Robinson K, Cardasis H, Stevens S, Sellers JR, Battelle BA. Loop 2 of limulus myosin III is phosphorylated by protein kinase A and autophosphorylation. Biochemistry 2007; 46:4280-93. [PMID: 17367164 PMCID: PMC2580675 DOI: 10.1021/bi062112u] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Little is known about the functions of class III unconventional myosins although, with an N-terminal kinase domain, they are potentially both signaling and motor proteins. Limulus myosin III is particularly interesting because it is a phosphoprotein abundant in photoreceptors that becomes more heavily phosphorylated at night by protein kinase A. This enhanced nighttime phosphorylation occurs in response to signals from an endogenous circadian clock and correlates with dramatic changes in photoreceptor structure and function. We seek to understand the role of Limulus myosin III and its phosphorylation in photoreceptors. Here we determined the sites that become phosphorylated in Limulus myosin III and investigated its kinase, actin binding, and myosin ATPase activities. We show that Limulus myosin III exhibits kinase activity and that a major site for both protein kinase A and autophosphorylation is located within loop 2 of the myosin domain, an important actin binding region. We also identify the phosphorylation of an additional protein kinase A and autophosphorylation site near loop 2, and a predicted phosphorylation site within loop 2. We show that the kinase domain of Limulus myosin III shares some pharmacological properties with protein kinase A, and that it is a potential opsin kinase. Finally, we demonstrate that Limulus myosin III binds actin but lacks ATPase activity. We conclude that Limulus myosin III is an actin-binding and signaling protein and speculate that interactions between actin and Limulus myosin III are regulated by both second messenger mediated phosphorylation and autophosphorylation of its myosin domain within and near loop 2.
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Affiliation(s)
- Karen Kempler
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
| | - Judit Tóth
- Department of Biochemistry, Eötvös Loránd University Pázmány P.s. 1/c. Budapest 1117, Hungary
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-1762
| | - Roxanne Yamashita
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-1762
| | - Gretchen Mapel
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
| | - Kimberly Robinson
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
| | - Helene Cardasis
- Proteomics Core of the ICBR, University of Florida, Gainesville 32010
- Department of Chemistry, University of Florida, Gainesville 32010
| | - Stanley Stevens
- Proteomics Core of the ICBR, University of Florida, Gainesville 32010
| | - James R. Sellers
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-1762
| | - Barbara-Anne Battelle
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
- CORRESPONDING AUTHOR: Barbara-Anne Battelle, Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd. St. Augustine, FL 32080. Tel. 904-461-4022; Fax 904-461-008;
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Ahmad ST, Natochin M, Artemyev NO, O'Tousa JE. The Drosophila rhodopsin cytoplasmic tail domain is required for maintenance of rhabdomere structure. FASEB J 2006; 21:449-55. [PMID: 17158966 DOI: 10.1096/fj.06-6530com] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ninaE-encoded Rh1 rhodopsin is the major light-sensitive pigment expressed in Drosophila R1-6 photoreceptor cells. Rh1 rhodopsin localizes to and is essential for the development and maintenance of the rhabdomere, the specialized membrane-rich organelle that serves as the site of phototransduction. We showed previously that the vertebrate bovine rhodopsin (Rho) is expressed and properly localized in Drosophila photoreceptor cells. Drosophila photoreceptors expressing only Rho have normal rhabdomere structure at young ages, but the rhabdomeres are not maintained and show extensive disorganization by 7-10 days of age. A series of Rho-Rh1 opsin chimeric rhodopsins were used to identify Rh1 domains required for maintenance of rhabdomeric structure. The results show that the Rh1 rhodopsin cytoplasmic tail domain, positioned to interact with cytoplasmic structural components, plays a major role in promoting rhabdomeric organization.
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Affiliation(s)
- Syed Tariq Ahmad
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
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