Nuclear Softness Promotes the Metastatic Potential of Large-Nucleated Colorectal Cancer Cells via the ErbB4-Akt1-Lamin A/C Signaling Pathway.

Abnormal nuclear enlargement is a diagnostic and physical hallmark of malignant tumors. Large nuclei are positively associated with an increased risk of developing metastasis; however, a large nucleus is inevitably more resistant to cell migration due to its size. The present study demonstrated that the nuclear size of primary colorectal cancer (CRC) cells at an advanced stage was larger than cells at an early stage. In addition, the nuclei of CRC liver metastases were larger than those of the corresponding primary CRC tissues. CRC cells were sorted into large-nucleated cells (LNCs) and small-nucleated cells (SNCs). Purified LNCs exhibited greater constricted migratory and metastatic capacity than SNCs in vitro and in vivo. Mechanistically, ErbB4 was highly expressed in LNCs, which phosphorylated lamin A/C at serine 22 via the ErbB4-Akt1 signaling pathway. Furthermore, the level of phosphorylated lamin A/C was a negative determinant of nuclear stiffness. Taken together, CRC LNCs possessed greater constricted migratory and metastatic potential than SNCs due to ErbB4-Akt1-mediated lamin A/C phosphorylation and nuclear softening. These results may provide a potential treatment strategy for tumor metastasis by targeting nuclear stiffness in patients with cancer, particularly CRC.

Perinuclear damage from nuclear envelope deterioration elicits stress responses that contribute to LMNA cardiomyopathy.

Mutations in the LMNA gene encoding lamins A/C cause an array of tissue-selective diseases, with the heart being the most commonly affected organ. Despite progress in understanding the perturbations emanating from LMNA mutations, an integrative understanding of the pathogenesis underlying cardiac dysfunction remains elusive. Using a novel conditional deletion model capable of translatome profiling, we observed that cardiomyocyte-specific Lmna deletion in adult mice led to rapid cardiomyopathy with pathological remodeling. Before cardiac dysfunction, Lmna-deleted cardiomyocytes displayed nuclear abnormalities, Golgi dilation/fragmentation, and CREB3-mediated stress activation. Translatome profiling identified MED25 activation, a transcriptional cofactor that regulates Golgi stress. Autophagy is disrupted in the hearts of these mice, which can be recapitulated by disrupting the Golgi. Systemic administration of modulators of autophagy or ER stress significantly delayed cardiac dysfunction and prolonged survival. These studies support a hypothesis wherein stress responses emanating from the perinuclear space contribute to the LMNA cardiomyopathy development.

Acquired NF2 mutation confers resistance to TRK inhibition in an ex vivo LMNA::NTRK1-rearranged soft-tissue sarcoma cell model.

Genomic rearrangements of the neurotrophic receptor tyrosine kinase genes (NTRK1, NTRK2, and NTRK3) are the most common mechanism of oncogenic activation for this family of receptors, resulting in sustained cancer cell proliferation. Several targeted therapies have been approved for tumours harbouring NTRK fusions and a new generation of TRK inhibitors has already been developed due to acquired resistance. We established a patient-derived LMNA::NTRK1-rearranged soft-tissue sarcoma cell model ex vivo with an acquired resistance to targeted TRK inhibition. Molecular profiling of the resistant clones revealed an acquired NF2 loss of function mutation that was absent in the parental cell model. Parental cells showed continuous sensitivity to TRK-targeted treatment, whereas the resistant clones were insensitive. Furthermore, resistant clones showed upregulation of the MAPK and mTOR/AKT pathways in the gene expression based on RNA sequencing data and increased sensitivity to MEK and mTOR inhibitor therapy. Drug synergy was seen using trametinib and rapamycin in combination with entrectinib. Medium-throughput drug screening further identified small compounds as potential drug candidates to overcome resistance as monotherapy or in combination with entrectinib. In summary, we developed a comprehensive model of drug resistance in an LMNA::NTRK1-rearranged soft-tissue sarcoma and have broadened the understanding of acquired drug resistance to targeted TRK therapy. Furthermore, we identified drug combinations and small compounds to overcome acquired drug resistance and potentially guide patient care in a functional precision oncology setting. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Exacerbated atherosclerosis in progeria is prevented by progerin elimination in vascular smooth muscle cells but not endothelial cells.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare disease caused by the expression of progerin, a mutant protein that accelerates aging and precipitates death. Given that atherosclerosis complications are the main cause of death in progeria, here, we investigated whether progerin-induced atherosclerosis is prevented in HGPSrev-Cdh5-CreERT2 and HGPSrev-SM22α-Cre mice with progerin suppression in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), respectively. HGPSrev-Cdh5-CreERT2 mice were undistinguishable from HGPSrev mice with ubiquitous progerin expression, in contrast with the ameliorated progeroid phenotype of HGPSrev-SM22α-Cre mice. To study atherosclerosis, we generated atheroprone mouse models by overexpressing a PCSK9 gain-of-function mutant. While HGPSrev-Cdh5-CreERT2 and HGPSrev mice developed a similar level of excessive atherosclerosis, plaque development in HGPSrev-SM22α-Cre mice was reduced to wild-type levels. Our studies demonstrate that progerin suppression in VSMCs, but not in ECs, prevents exacerbated atherosclerosis in progeroid mice.

mTOR Inhibition Prolongs Survival and Has Beneficial Effects on Heart Function After Onset of Lamin A/C Gene Mutation Cardiomyopathy in Mice.

BACKGROUND: Mutations in LMNA encoding nuclear envelope proteins lamin A/C cause dilated cardiomyopathy. Activation of the AKT/mTOR (RAC-α serine/threonine-protein kinase/mammalian target of rapamycin) pathway is implicated as a potential pathophysiologic mechanism. The aim of this study was to assess whether pharmacological inhibition of mTOR signaling has beneficial effects on heart function and prolongs survival in a mouse model of the disease, after onset of heart failure. METHODS: We treated male LmnaH222P/H222P mice, after the onset of heart failure, with placebo or either of 2 orally bioavailable mTOR inhibitors: everolimus or NV-20494, a rapamycin analog highly selective against mTORC1. We examined left ventricular remodeling, and the cell biological, biochemical, and histopathologic features of cardiomyopathy, potential drug toxicity, and survival. RESULTS: Everolimus treatment (n=17) significantly reduced left ventricular dilatation and increased contractility on echocardiography, with a 7% (P=0.018) reduction in left ventricular end-diastolic diameter and a 39% (P=0.0159) increase fractional shortening compared with placebo (n=17) after 6 weeks of treatment. NV-20494 treatment (n=15) yielded similar but more modest and nonsignificant changes. Neither drug prevented the development of cardiac fibrosis. Drug treatment reactivated suppressed autophagy and inhibited mTORC1 signaling in the heart, although everolimus was more potent. With regards to drug toxicity, everolimus alone led to a modest degree of glucose intolerance during glucose challenge. Everolimus (n=20) and NV-20494 (n=20) significantly prolonged median survival in LmnaH222P/H222P mice, by 9% (P=0.0348) and 11% (P=0.0206), respectively, compared with placebo (n=20). CONCLUSIONS: These results suggest that mTOR inhibitors may be beneficial in patients with cardiomyopathy caused by LMNA mutations and that further study is warranted.

Doxorubicin induces phosphorylation of lamin A/C and loss of nuclear membrane integrity: A novel mechanism of cardiotoxicity.

Lamin A/C, essential inner nuclear membrane proteins, have been linked to progeria, a disease of accelerated aging, and many other diseases, which include cardiac disorder. Lamin A/C mutation and its phosphorylation are associated with altering nuclear shape and size. The role of lamin A/C in regulating normal cardiac function was reported earlier. In the present study, we hypothesized that Doxorubicin (Dox) may alter total lamin A/C expression and phosphorylation, thereby taking part in cardiac injury. An in vitro cellular injury model was generated with Dox (0.1-10.0 µM) treatment on cardiomyoblast cells (H9c2) to prove our hypothesis. Increased size and irregular (ameboid) nucleus shape were observed in H9c2 cells after Dox treatment. Similarly, we have observed a significant increase in cell death on increasing the Dox concentration. The expression of lamin A/C and its phosphorylation at serine 22 significantly decreased and increased, respectively in H9c2 cells and rat hearts after Dox exposure. Phosphorylation led to depolymerization of the lamin A/C in the inner nuclear membrane and was evidenced by their presence throughout the nucleoplasm as observed by immunocytochemistry techniques. Thinning and perforation on the walls of the nuclear membrane were observed in Dox-treated H9c2 cells. LMNA-overexpression in H9c2 protected the cells from Dox-induced cell death, reversing all changes described above. Further, improvement of lamin A/C levels was observed in Dox-treated H9c2 cells when treated with Purvalanol A, a CDK1 inhibitor and N-acetylcysteine, an antioxidant. The study provides new insight regarding Dox-induced cardiac injury with the involvement of lamin A/C and alteration of inner nuclear membrane structure.

Defective prelamin A processing promotes unconventional necroptosis driven by nuclear RIPK1.

Defects in the prelamin A processing enzyme caused by loss-of-function mutations in the ZMPSTE24 gene are responsible for a spectrum of progeroid disorders characterized by the accumulation of farnesylated prelamin A. Here we report that defective prelamin A processing triggers nuclear RIPK1-dependent signalling that leads to necroptosis and inflammation. We show that accumulated prelamin A recruits RIPK1 to the nucleus to facilitate its activation upon tumour necrosis factor stimulation in ZMPSTE24-deficient cells. Kinase-activated RIPK1 then promotes RIPK3-mediated MLKL activation in the nucleus, leading to nuclear envelope disruption and necroptosis. This signalling relies on prelamin A farnesylation, which anchors prelamin A to nuclear envelope to serve as a nucleation platform for necroptosis. Genetic inactivation of necroptosis ameliorates the progeroid phenotypes in Zmpste24-/- mice. Our findings identify an unconventional nuclear necroptosis pathway resulting from ZMPSTE24 deficiency with pathogenic consequences in progeroid disorder and suggest RIPK1 as a feasible target for prelamin A-associated progeroid disorders.

Lamin B1 curtails early human papillomavirus infection by safeguarding nuclear compartmentalization and autophagic capacity.

Human papillomavirus (HPV) infection is a primary cause of cervical and head-and-neck cancers. The HPV genome enters the nucleus during mitosis when the nuclear envelope disassembles. Given that lamins maintain nuclear integrity during interphase, we asked to what extent their loss would affect early HPV infection. To address this question, we infected human cervical cancer cells and keratinocytes lacking the major lamins with a HPV16 pseudovirus (HP-PsV) encoding an EGFP reporter. We found that a sustained reduction or complete loss of lamin B1 significantly increased HP-PsV infection rate. A corresponding greater nuclear HP-PsV load in LMNB1 knockout cells was directly related to their prolonged mitotic window and extensive nuclear rupture propensity. Despite the increased HP-PsV presence, EGFP transcript levels remained virtually unchanged, indicating an additional defect in protein turnover. Further investigation revealed that LMNB1 knockout led to a substantial decrease in autophagic capacity, possibly linked to the persistent activation of cGAS by cytoplasmic chromatin exposure. Thus, the attrition of lamin B1 increases nuclear perviousness and attenuates autophagic capacity, creating an environment conducive to unrestrained accumulation of HPV capsids. Our identification of lower lamin B1 levels and nuclear BAF foci in the basal epithelial layer of several human cervix samples suggests that this pathway may contribute to an increased individual susceptibility to HPV infection.

Depletion of lamins B1 and B2 promotes chromatin mobility and induces differential gene expression by a mesoscale-motion-dependent mechanism.

BACKGROUND: B-type lamins are critical nuclear envelope proteins that interact with the three-dimensional genomic architecture. However, identifying the direct roles of B-lamins on dynamic genome organization has been challenging as their joint depletion severely impacts cell viability. To overcome this, we engineered mammalian cells to rapidly and completely degrade endogenous B-type lamins using Auxin-inducible degron technology. RESULTS: Using live-cell Dual Partial Wave Spectroscopic (Dual-PWS) microscopy, Stochastic Optical Reconstruction Microscopy (STORM), in situ Hi-C, CRISPR-Sirius, and fluorescence in situ hybridization (FISH), we demonstrate that lamin B1 and lamin B2 are critical structural components of the nuclear periphery that create a repressive compartment for peripheral-associated genes. Lamin B1 and lamin B2 depletion minimally alters higher-order chromatin folding but disrupts cell morphology, significantly increases chromatin mobility, redistributes both constitutive and facultative heterochromatin, and induces differential gene expression both within and near lamin-associated domain (LAD) boundaries. Critically, we demonstrate that chromatin territories expand as upregulated genes within LADs radially shift inwards. Our results indicate that the mechanism of action of B-type lamins comes from their role in constraining chromatin motion and spatial positioning of gene-specific loci, heterochromatin, and chromatin domains. CONCLUSIONS: Our findings suggest that, while B-type lamin degradation does not significantly change genome topology, it has major implications for three-dimensional chromatin conformation at the single-cell level both at the lamina-associated periphery and the non-LAD-associated nuclear interior with concomitant genome-wide transcriptional changes. This raises intriguing questions about the individual and overlapping roles of lamin B1 and lamin B2 in cellular function and disease.

From gene to mechanics: a comprehensive insight into the mechanobiology of LMNA mutations in cardiomyopathy.

Severe cardiac remodeling leading to heart failure in individuals harboring pathogenic LMNA variants, known as cardiolaminopathy, poses a significant clinical challenge. Currently, there is no effective treatment for lamin-related diseases. Exploring the intricate molecular landscape underlying this condition, with a specific focus on abnormal mechanotransduction, will propel our understanding of cardiolaminopathy. The LMNA gene undergoes alternative splicing to create A-type lamins, a part of the intermediate filament protein family. A-type lamins are located underneath the nuclear envelope, and given their direct interaction with chromatin, they serve as mechanosensory of the cell by interacting with the cytoskeleton and safeguarding the transcriptional program of cells. Nucleated cells in the cardiovascular system depend on precise mechanical cues for proper function and adaptation to stress. Mechanosensitive signaling pathways are essential in regulating mechanotransduction. They play a pivotal role in various molecular and cellular processes and commence numerous downstream effects, leading to transcriptional activation of target genes involved in proliferation, migration, and (anti-)apoptosis. Most pathways are known to be regulated by kinases, and this area remains largely understudied in cardiomyopathies.Heart failure is linked to disrupted mechanotransduction, where LMNA mutations affect nuclear integrity, impacting the response to extracellular matrix signals and the environment. The Hippo pathway, anchored by YAP1/WWTR1, emerges as a central player by orchestrating cellular responses to mechanical signals. However, the involvement of Hippo and YAP1/WWTR1 in cardiolaminopathy is unclear and likely mutation- and tissue-specific, warranting further investigation. Here, we highlight the involvement of multiple signaling pathways in mechanotransduction in cardiolaminopathy. We delve into (non-)canonical functions of key signaling components, which may hold critical clues for understanding disease pathogenesis. In summary, we comprehensively examine the mechanobiology of A-type lamins, the role of mechanosensitive signaling pathways, and their intricate interplay in the pathogenesis of cardiolaminopathy. A better understanding of these mechanisms is paramount for developing targeted therapies and interventions for individuals afflicted with this debilitating cardiac condition. Prior studies overlooked accurate gene nomenclature in protein and pathway names. Our review addresses this gap, ensuring precision by aligning names with correct gene nomenclature.

Mutations in the A-type lamin gene (LMNA) can cause a laminopathy. A specific manifestation of this disease leads to cardiolaminopathy, a serious heart condition. The lamin network, located at the inner nuclear membrane, is a central player in transforming forces within cells. As cells move and function, they rely on the ability to sense and respond to these forces, a process named mechanosensing and -response. This review provides an overview of the key molecular pathways involved in the development of heart failure. The molecular mechanisms underlying LMNA cardiomyopathy are poorly understood because the interaction between the signaling pathways is challenging to elucidate. Deciphering these pathways is key to understanding the underlying mechanisms of disease and finding novel targets to alter the pathways and lessen the symptoms of diseases.

Lamin A/C and PI(4,5)P2-A Novel Complex in the Cell Nucleus.

Lamins, the nuclear intermediate filaments, are important regulators of nuclear structural integrity as well as nuclear functional processes such as DNA transcription, replication and repair, and epigenetic regulations. A portion of phosphorylated lamin A/C localizes to the nuclear interior in interphase, forming a lamin A/C pool with specific properties and distinct functions. Nucleoplasmic lamin A/C molecular functions are mainly dependent on its binding partners; therefore, revealing new interactions could give us new clues on the lamin A/C mechanism of action. In the present study, we show that lamin A/C interacts with nuclear phosphoinositides (PIPs), and with nuclear myosin I (NM1). Both NM1 and nuclear PIPs have been previously reported as important regulators of gene expression and DNA damage/repair. Furthermore, phosphorylated lamin A/C forms a complex with NM1 in a phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2)-dependent manner in the nuclear interior. Taken together, our study reveals a previously unidentified interaction between phosphorylated lamin A/C, NM1, and PI(4,5)P2 and suggests new possible ways of nucleoplasmic lamin A/C regulation, function, and importance for the formation of functional nuclear microdomains.

Proteomic characterization of human LMNA-related congenital muscular dystrophy muscle cells.

LMNA-related congenital muscular dystrophy (L-CMD) is caused by mutations in the LMNA gene, encoding lamin A/C. To further understand the molecular mechanisms of L-CMD, proteomic profiling using DIA mass spectrometry was conducted on immortalized myoblasts and myotubes from controls and L-CMD donors each harbouring a different LMNA mutation (R249W, del.32 K and L380S). Compared to controls, 124 and 228 differentially abundant proteins were detected in L-CMD myoblasts and myotubes, respectively, and were associated with enriched canonical pathways including synaptogenesis and necroptosis in myoblasts, and Huntington's disease and insulin secretion in myotubes. Abnormal nuclear morphology and reduced lamin A/C and emerin abundance was evident in all L-CMD cell lines compared to controls, while nucleoplasmic aggregation of lamin A/C was restricted to del.32 K cells, and mislocalization of emerin was restricted to R249W cells. Abnormal nuclear morphology indicates loss of nuclear lamina integrity as a common feature of L-CMD, likely rendering muscle cells vulnerable to mechanically induced stress, while differences between L-CMD cell lines in emerin and lamin A localization suggests that some molecular alterations in L-CMD are mutation specific. Nonetheless, identifying common proteomic alterations and molecular pathways across all three L-CMD lines has highlighted potential targets for the development of non-mutation specific therapies.

Protein kinase C activity modulates nuclear Lamin A/C dynamics in HeLa cells.

The nuclear lamina serves important functions in the nucleus, providing structural support to the nuclear envelope and contributing to chromatin organization. The primary proteins that constitute the lamina are nuclear lamins whose functions are impacted by post-translational modifications, including phosphorylation by protein kinase C (PKC). While PKC-mediated lamin phosphorylation is important for nuclear envelope breakdown during mitosis, less is known about interphase roles for PKC in regulating nuclear structure. Here we show that overexpression of PKC ß, but not PKC α, increases the Lamin A/C mobile fraction in the nuclear envelope in HeLa cells without changing the overall structure of Lamin A/C and Lamin B1 within the nuclear lamina. Conversely, knockdown of PKC ß, but not PKC α, reduces the Lamin A/C mobile fraction. Thus, we demonstrate an isoform-specific role for PKC in regulating interphase Lamin A/C dynamics outside of mitosis.

Targeting Nuclear Mechanics Mitigates the Fibroblast Invasiveness in Pathological Dermal Scars Induced by Matrix Stiffening.

Pathological dermal scars such as keloids present significant clinical challenges lacking effective treatment options. Given the distinctive feature of highly stiffened scar tissues, deciphering how matrix mechanics regulate pathological progression can inform new therapeutic strategies. Here, it is shown that pathological dermal scar keloid fibroblasts display unique metamorphoses to stiffened matrix. Compared to normal fibroblasts, keloid fibroblasts show high sensitivity to stiffness rather than biochemical stimulation, activating cytoskeletal-to-nuclear mechanosensing molecules. Notably, keloid fibroblasts on stiff matrices exhibit nuclear softening, concomitant with reduced lamin A/C expression, and disrupted anchoring of lamina-associated chromatin. This nuclear softening, combined with weak adhesion and high contractility, facilitates the invasive migration of keloid fibroblasts through confining matrices. Inhibiting lamin A/C-driven nuclear softening, via lamin A/C overexpression or actin disruption, mitigates such invasiveness of keloid fibroblasts. These findings highlight the significance of the nuclear mechanics of keloid fibroblasts in scar pathogenesis and propose lamin A/C as a potential therapeutic target for managing pathological scars.

Nucleocytoplasmic shuttling of BEFV M protein-modulated by lamin A/C and chromosome maintenance region 1 through a transcription-, carrier- and energy-dependent pathway.

This study demonstrates for the first time that the matrix (M) protein of BEFV is a nuclear targeting protein that shuttles between the nucleus and the cytoplasm in a transcription-, carrier-, and energy-dependent manner. Experiments performed in both intact cells and digitonin-permeabilized cells revealed that M protein targets the nucleolus and requires carrier, cytosolic factors or energy input. By employing sequence and mutagenesis analyses, we have determined both nuclear localization signal (NLS) 6KKGKSK11 and nuclear export signal (NES) 98LIITSYL TI106 of M protein that are important for the nucleocytoplasmic shuttling of M protein. Furthermore, we found that both lamin A/C and chromosome maintenance region 1 (CRM-1) proteins could be coimmunoprecipitated and colocalized with the BEFV M protein. Knockdown of lamin A/C by shRNA and inhibition of CRM-1 by leptomycin B significantly reduced virus yield. Collectively, this study provides novel insights into nucleocytoplasmic shuttling of the BEFV M protein modulated by lamin A/C and CRM-1 and by a transcription- and carrier- and energy-dependent pathway.

Lamin A K97E leads to NF-κB-mediated dysfunction of inflammatory responses in dilated cardiomyopathy.

BACKGROUND INFORMATION: Lamins are type V intermediate filament proteins underlying the inner nuclear membrane which provide structural rigidity to the nucleus, tether the chromosomes, maintain nuclear homeostasis, and remain dynamically associated with developmentally regulated regions of the genome. A large number of mutations particularly in the LMNA gene encoding lamin A/C results in a wide array of human diseases, collectively termed as laminopathies. Dilated Cardiomyopathy (DCM) is one such laminopathic cardiovascular disease which is associated with systolic dysfunction of left or both ventricles leading to cardiac arrhythmia which ultimately culminates into myocardial infarction. RESULTS: In this work, we have unraveled the epigenetic landscape to address the regulation of gene expression in mouse myoblast cell line in the context of the missense mutation LMNA 289A

The structure and function of lamin A/C: Special focus on cardiomyopathy and therapeutic interventions.

Lamins are inner nuclear membrane proteins that belong to the intermediate filament family. Lamin A/C lie adjacent to the heterochromatin structure in polymer form, providing skeletal to the nucleus. Based on the localization, lamin A/C provides nuclear stability and cytoskeleton to the nucleus and modulates chromatin organization and gene expression. Besides being the structural protein making the inner nuclear membrane in polymer form, lamin A/C functions as a signalling molecule involved in gene expression as an enhancer inside the nucleus. Lamin A/C regulates various cellular pathways like autophagy and energy balance in the cytoplasm. Its expression is highly variable in differentiated tissues, higher in hard tissues like bone and muscle cells, and lower in soft tissues like the liver and brain. In muscle cells, including the heart, lamin A/C must be expressed in a balanced state. Lamin A/C mutation is linked with various diseases, such as muscular dystrophy, lipodystrophy, and cardiomyopathies. It has been observed that a good number of mutations in the LMNA gene impact cardiac activity and its function. Although several works have been published, there are still several unexplored areas left regarding the lamin A/C function and structure in the cardiovascular system and its pathological state. In this review, we focus on the structural organization, expression pattern, and function of lamin A/C, its interacting partners, and the pathophysiology associated with mutations in the lamin A/C gene, with special emphasis on cardiovascular diseases. With the recent finding on lamin A/C, we have summarized the possible therapeutic interventions to treat cardiovascular symptoms and reverse the molecular changes.

ABHD7-mediated depalmitoylation of lamin A promotes myoblast differentiation.

LMNA gene mutation can cause muscular dystrophy, and post-translational modification plays a critical role in regulating its function. Here, we identify that lamin A is palmitoylated at cysteine 522, 588, and 591 residues, which are reversely catalyzed by palmitoyltransferase zinc finger DHHC-type palmitoyltransferase 5 (ZDHHC5) and depalmitoylase α/ß hydrolase domain 7 (ABHD7). Furthermore, the metabolite lactate promotes palmitoylation of lamin A by inhibiting the interaction between it and ABHD7. Interestingly, low-level palmitoylation of lamin A promotes, whereas high-level palmitoylation of lamin A inhibits, murine myoblast differentiation. Together, these observations suggest that ABHD7-mediated depalmitoylation of lamin A controls myoblast differentiation.

N6-Methyladenosine Modification of lncCCKAR-5 Regulates Autophagy in Human Umbilical Cord Mesenchymal Stem Cells by Destabilizing LMNA and Inhibits Diabetic Wound Healing.

Long noncoding RNAs are pivotal contributors to the development of human diseases. However, their significance in the context of diabetic wound healing regulated by human umbilical cord mesenchymal stem cells (hUCMSCs) remains unclear. This study sheds light on the involvement of lncCCKAR5 in this process. We found that hUCMSCs exposed to high glucose conditions exhibited a significant downregulation of lncCCKAR5 expression, and lncCCKAR5 played a critical role in modulating autophagy, thus inhibiting apoptosis in hUCMSCs. In addition, the reduction of lncCCKAR5 in cells exposed to high glucose effectively thwarted cellular senescence and facilitated filopodium formation. Mechanistically, lncCCKAR5 served as a scaffold that facilitated the interaction between MKRN2 and LMNA, a key regulator of cytoskeletal function and autophagy. The lncCCKAR5/LMNA/MKRN2 complex played a pivotal role in promoting the ubiquitin-mediated degradation of LMNA, with this effect being further augmented by N6-adenosine methylation of lncCCKAR5. Consequently, our findings underscore the critical role of lncCCKAR5 in regulating the autophagic process in hUCMSCs, particularly through protein ubiquitination and degradation. This intricate regulatory network presents a promising avenue for potential therapeutic interventions in the context of diabetic wound healing involving hUCMSCs.

p300 nucleocytoplasmic shuttling underlies mTORC1 hyperactivation in Hutchinson-Gilford progeria syndrome.

The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth, metabolism and autophagy. Multiple pathways modulate mTORC1 in response to nutrients. Here we describe that nucleus-cytoplasmic shuttling of p300/EP300 regulates mTORC1 activity in response to amino acid or glucose levels. Depletion of these nutrients causes cytoplasm-to-nucleus relocalization of p300 that decreases acetylation of the mTORC1 component raptor, thereby reducing mTORC1 activity and activating autophagy. This is mediated by AMP-activated protein kinase-dependent phosphorylation of p300 at serine 89. Nutrient addition to starved cells results in protein phosphatase 2A-dependent dephosphorylation of nuclear p300, enabling its CRM1-dependent export to the cytoplasm to mediate mTORC1 reactivation. p300 shuttling regulates mTORC1 in most cell types and occurs in response to altered nutrients in diverse mouse tissues. Interestingly, p300 cytoplasm-nucleus shuttling is altered in cells from patients with Hutchinson-Gilford progeria syndrome. p300 mislocalization by the disease-causing protein, progerin, activates mTORC1 and inhibits autophagy, phenotypes that are normalized by modulating p300 shuttling. These results reveal how nutrients regulate mTORC1, a cytoplasmic complex, by shuttling its positive regulator p300 in and out of the nucleus, and how this pathway is misregulated in Hutchinson-Gilford progeria syndrome, causing mTORC1 hyperactivation and defective autophagy.