Spatial distribution of lamin A/C determines nuclear stiffness and stress-mediated deformation

While diverse cellular components have been identified as mechanotransduction elements, the deformation of the nucleus itself is a critical mechanosensory mechanism, implying that nuclear stiffness is essential in determining responses to intracellular and extracellular stresses. Though the nuclear membrane protein lamin A/C is known to contribute to nuclear stiffness, bulk moduli of nuclei have not been reported for various levels of lamin A/C. Here we measure the nuclear bulk moduli as a function of lamin A/C expression and applied osmotic stress, revealing a linear dependence within the range of 2-4 MegaPascal (MPa). We also find that the nuclear compression is anisotropic, with the vertical axis of the nucleus being more compliant than the minor and major axes in the substrate plane. We then related the spatial distribution of lamin A/C with sub-micron 3D nuclear envelope deformation, revealing that local areas of the nuclear envelope with higher density of lamin A/C have correspondingly lower local deformations. These findings describe the complex dispersion of nuclear deformations as a function of lamin A/C expression and distribution, implicating a lamin A/C role in mechanotransduction.

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Spatial distribution of lamin A determines nuclear stiffness and stress-mediated deformation

10.1101/765263 ◽

2019 ◽

Author(s):

Luv Kishore Srivastava ◽

Zhaoping Ju ◽

Ajinkya Ghagre ◽

Allen J. Ehrlicher

Keyword(s):

Spatial Distribution ◽

Nuclear Envelope ◽

Bulk Modulus ◽

Quantitative Relationship ◽

Major Axis ◽

Vertical Axis ◽

Lamin A ◽

Expression Levels ◽

Nuclear Mechanics ◽

Dominant Component

AbstractThe nucleus is the largest organelle and information center of the cell; while diverse cellular components have been identified as mechanotransduction elements, the deformation of the nucleus itself is emerging as a critical mechanosensory mechanism, suggesting that the nuclear stiffness is essential in determining responses to intracellular and extracellular stresses. The nuclear membrane protein, lamin A, is known to be a dominant component in nuclear stiffening; however, the quantitative relationship between lamin A expression and nuclear deformation is still unclear. Here we measure the nuclear moduli as a function of lamin A expression and applied stress, revealing a linear dependence of bulk modulus on lamin A expression. We also find that the bulk modulus is anisotropic, with the vertical axis of the nucleus being more compliant than the minor and major axis. To examine how lamin A influences nuclear mechanics at the sub-micron scale we correlated the spatial distribution of lamin A with 3D nuclear envelope deformation, revealing that local areas of the nuclear envelope with higher expression levels of lamin A have correspondingly lower local deformations, and that increased lamin A expression levels result in a narrower distribution of smaller deformations. These findings describe the complex dispersion of nuclear deformations as a function of lamin A expression and distribution and implicate a role in mechanotransduction.

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Novel missense alleles of SIGMAR1 as tools to understand emerin-dependent gene silencing in response to cocaine

Experimental Biology and Medicine ◽

10.1177/1535370219863444 ◽

2019 ◽

Vol 244 (15) ◽

pp. 1354-1361 ◽

Cited By ~ 2

Author(s):

Adith S Arun ◽

Chelsy R Eddings ◽

Katherine L Wilson

Keyword(s):

Membrane Protein ◽

Nuclear Envelope ◽

Nuclear Lamina ◽

Drug Binding ◽

Lamin A ◽

Human Populations ◽

East Asians ◽

Sigma 1 Receptor ◽

Missense Variants ◽

Sigma 1

Sigma-1 receptor (Sigma1R; SIGMAR1), an integral membrane protein of the endoplasmic reticulum and nuclear envelope, has a hydrophobic drug-binding pocket that binds with high affinity to addictive drugs (cocaine, methamphetamine) and therapeutics used to treat a wide spectrum of neurological disorders. Cocaine enhances Sigma1R association with three nuclear lamina proteins (emerin, lamin A/C, BANF1), causing Sigma1R-dependent and emerin-dependent recruitment and transcriptional repression of a gene, MAOB1, involved in dopamine removal from neural synapses. The mechanism of Sigma1R association with emerin and the molecular impact of cocaine on their association are unknown. Mutations in Sigma1R, as a proposed regulator or mis-regulator of the nuclear lamina, have the potential to alter nuclear lamina function in brain or other tissues. We examined the frequency of SIGMAR1 missense alleles among 60,706 unrelated individuals in the ExAC database. We identified two novel SIGMAR1 missense variants of particular interest due to their frequency and potential to impact molecular association with emerin or other nuclear lamina proteins. Variant p.Q2P was widespread in ExAC (overall allele frequency 18.4%) with broad ethnic distribution among non-Finnish Europeans, Africans, South Asians, Latinx (allele frequencies ∼15% to 23%), and East Asians (∼38%). The p.R208W allele was identified in ∼0.78% of individuals overall with enrichment in Africans, Latinx, and East Asians (∼1.9–2.9%). These and other novel Sigma1R variants provide tools for future studies to determine the molecular basis of Sigma1R association with emerin and the mechanism of nuclear lamina misregulation by cocaine and potentially other Sigma1R agonists. Impact statement The Sigma-1 Receptor (Sigma1R; SIGMAR1) binds neuroactive drugs—both therapeutic and addictive—and associates with the nuclear membrane protein emerin and its partners lamin A/C and BANF1 in response to cocaine, through unknown mechanisms. We identified two novel SIGMAR1 missense variants of special interest due to their prevalence in human populations and their potential to perturb Sigma1R function at the nuclear envelope. Despite its importance in physiology and pharmacology, many aspects of Sigma1R including its membrane topology are unclear. Our findings lay the foundation for future molecular studies to understand how Sigma1R associates with emerin, lamin A/C, and BANF1 and manipulates their activity in response to agonist.

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Alterations of nuclear envelope and chromatin organization in mandibuloacral dysplasia, a rare form of laminopathy

Physiological Genomics ◽

10.1152/physiolgenomics.00060.2005 ◽

2005 ◽

Vol 23 (2) ◽

pp. 150-158 ◽

Cited By ~ 80

Author(s):

Ilaria Filesi ◽

Francesca Gullotta ◽

Giovanna Lattanzi ◽

Maria Rosaria D'Apice ◽

Cristina Capanni ◽

...

Keyword(s):

Nuclear Envelope ◽

Protein A ◽

Nuclear Architecture ◽

Mendelian Inheritance ◽

Premature Aging ◽

Lamin A ◽

Lamin B ◽

Lamin B Receptor ◽

Epigenetic Events ◽

Mandibuloacral Dysplasia

Autosomal recessive mandibuloacral dysplasia [mandibuloacral dysplasia type A (MADA); Online Mendelian Inheritance in Man (OMIM) no. 248370 ] is caused by a mutation in LMNA encoding lamin A/C. Here we show that this mutation causes accumulation of the lamin A precursor protein, a marked alteration of the nuclear architecture and, hence, chromatin disorganization. Heterochromatin domains are altered or completely lost in MADA nuclei, consistent with the finding that heterochromatin-associated protein HP1β and histone H3 methylated at lysine 9 and their nuclear envelope partner protein lamin B receptor (LBR) are delocalized and solubilized. Both accumulation of lamin A precursor and chromatin defects become more severe in older patients. These results strongly suggest that altered chromatin remodeling is a key event in the cascade of epigenetic events causing MADA and could be related to the premature-aging phenotype.

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A ternary membrane protein complex anchors the spindle pole body in the nuclear envelope in budding yeast

Journal of Biological Chemistry ◽

10.1074/jbc.m117.780601 ◽

2017 ◽

Vol 292 (20) ◽

pp. 8447-8458 ◽

Cited By ~ 10

Author(s):

Thomas Kupke ◽

Jörg Malsam ◽

Elmar Schiebel

Keyword(s):

Membrane Protein ◽

Nuclear Envelope ◽

Protein Complex ◽

Budding Yeast ◽

Spindle Pole Body ◽

Spindle Pole ◽

Membrane Protein Complex ◽

Pole Body

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Spatial distribution of lamin A and B1 in the K562 cell nuclear matrix stabilized with metal ions

Journal of Cellular Biochemistry ◽

10.1002/(sici)1097-4644(19991001)75:1<36::aid-jcb4>3.0.co;2-r ◽

1999 ◽

Vol 75 (1) ◽

pp. 36-45 ◽

Cited By ~ 11

Author(s):

Luca M. Neri ◽

Yves Raymond ◽

Antonio Giordano ◽

Paola Borgatti ◽

Marco Marchisio ◽

...

Keyword(s):

Spatial Distribution ◽

Metal Ions ◽

Nuclear Matrix ◽

K562 Cell ◽

Lamin A

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Function and assembly of nuclear pore complex proteins

Biochemistry and Cell Biology ◽

10.1139/o99-038 ◽

1999 ◽

Vol 77 (4) ◽

pp. 321-329 ◽

Cited By ~ 14

Author(s):

Khaldon Bodoor ◽

Sarah Shaikh ◽

Paul Enarson ◽

Sharmin Chowdhury ◽

Davide Salina ◽

...

Keyword(s):

Membrane Protein ◽

Nuclear Envelope ◽

Nuclear Pore Complex ◽

Nuclear Membrane ◽

Current View ◽

Nuclear Pore ◽

Dynamic Component ◽

Inner Nuclear Membrane ◽

Inner Nuclear Membrane Protein ◽

Nuclear Membrane Protein

Nuclear pore complexes (NPCs) are extremely elaborate structures that mediate the bidirectional movement of macromolecules between the nucleus and cytoplasm. The current view of NPC organization features a massive symmetrical framework that is embedded in the double membranes of the nuclear envelope. It embraces a central channel of as yet ill-defined structure but which may accommodate particles with diameters up to 26 nm provided that they bear specific import/export signals. Attached to both faces of the central framework are peripheral structures, short cytoplasmic filaments, and a nuclear basket assembly, which interact with molecules transiting the NPC. The mechanisms of assembly and the nature of NPC structural intermediates are still poorly understood. However, mutagenesis and expression studies have revealed discrete sequences within certain NPC proteins that are necessary and sufficient for their appropriate targeting. In addition, some details are emerging from observations on cells undergoing mitosis where the nuclear envelope is disassembled and its components, including NPC subunits, are dispersed throughout the mitotic cytoplasm. At the end of mitosis, all of these components are reutilized to form nuclear envelopes in the two daughter cells. To date, it has been possible to define a time course of postmitotic assembly for a group of NPC components (CAN/Nup214, Nup153, POM121, p62 and Tpr) relative to the integral inner nuclear membrane protein LAP2 and the NPC membrane glycoprotein gp210. Nup153, a dynamic component of the nuclear basket, associates with chromatin towards the end of anaphase coincident with, although independent of, the inner nuclear membrane protein, LAP2. Assembly of the remaining proteins follows that of the nuclear membranes and occurs in the sequence POM121, p62, CAN/Nup214 and gp210/Tpr. Since p62 remains as a complex with three other NPC proteins (p58, p54, p45) during mitosis, and CAN/Nup214 maintains a similar interaction with its partner, Nup84, the relative timing of assembly of these additional four proteins may also be inferred. These observations suggest that there is a sequential association of NPC proteins with chromosomes during nuclear envelope reformation and the recruitment of at least eight of these precedes that of gp210. These findings support a model in which it is POM121 rather than gp210 that defines initial membrane-associated NPC assembly intermediates and which may therefore represent an essential component of the central framework of the NPC. Key words: nuclear pore complex, nucleoporin, mitosis, nuclear transport

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Physiological and pathological roles of LRRK2 in the nuclear envelope integrity

Human Molecular Genetics ◽

10.1093/hmg/ddz245 ◽

2019 ◽

Vol 28 (23) ◽

pp. 3982-3996 ◽

Cited By ~ 3

Author(s):

Vered Shani ◽

Hazem Safory ◽

Raymonde Szargel ◽

Ninghan Wang ◽

Tsipora Cohen ◽

...

Keyword(s):

Nuclear Envelope ◽

Cortical Neurons ◽

Nuclear Lamina ◽

Lamin A ◽

Loss Of Function ◽

Function Mechanism ◽

Disease Mutations ◽

Lrrk2 G2019s ◽

Sporadic Parkinson’S Disease ◽

Seven In Absentia

Abstract Mutations in LRRK2 cause autosomal dominant and sporadic Parkinson’s disease, but the mechanisms involved in LRRK2 toxicity in PD are yet to be fully understood. We found that LRRK2 translocates to the nucleus by binding to seven in absentia homolog (SIAH-1), and in the nucleus it directly interacts with lamin A/C, independent of its kinase activity. LRRK2 knockdown caused nuclear lamina abnormalities and nuclear disruption. LRRK2 disease mutations mostly abolish the interaction with lamin A/C and, similar to LRRK2 knockdown, cause disorganization of lamin A/C and leakage of nuclear proteins. Dopaminergic neurons of LRRK2 G2019S transgenic and LRRK2 −/− mice display decreased circularity of the nuclear lamina and leakage of the nuclear protein 53BP1 to the cytosol. Dopaminergic nigral and cortical neurons of both LRRK2 G2019S and idiopathic PD patients exhibit abnormalities of the nuclear lamina. Our data indicate that LRRK2 plays an essential role in maintaining nuclear envelope integrity. Disruption of this function by disease mutations suggests a novel phosphorylation-independent loss-of-function mechanism that may synergize with other neurotoxic effects caused by LRRK2 mutations.

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