C2cd6-encoded CatSperτ Targets Sperm Calcium Channel to Ca2+ Signaling Domains in the Flagellar Membrane

In mammalian sperm cells, regulation of spatiotemporal Ca2+ signaling relies on the quadrilinear Ca2+ signaling nanodomains in the flagellar membrane. The sperm-specific, multi-subunit CatSper Ca2+ channel, which is crucial for sperm hyperactivated motility and male fertility, organizes the nanodomains. Here, we report CatSperτ, the C2cd6-encoded membrane-associating C2 domain protein, can independently migrate to the flagella and serve as a major targeting component of the CatSper channel complex. CatSperτ loss-of-function in mice demonstrates that it is essential for sperm hyperactivated motility and male fertility. CatSperτ targets the CatSper channel into the quadrilinear nanodomains in the flagella of developing spermatids, whereas it is dispensable for functional channel assembly. CatSperτ interacts with ciliary trafficking machinery in a C2-dependent manner. These findings provide insights into the CatSper channel trafficking to the Ca2+ signaling nanodomains and the shared molecular mechanisms of ciliary and flagellar membrane targeting.

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Molecular Bases of Human Malformation Syndromes Involving the SHH Pathway: GLIA/R Balance and Cardinal Phenotypes

International Journal of Molecular Sciences ◽

10.3390/ijms222313060 ◽

2021 ◽

Vol 22 (23) ◽

pp. 13060

Author(s):

Yo Niida ◽

Sumihito Togi ◽

Hiroki Ura

Keyword(s):

Molecular Mechanisms ◽

Brain Size ◽

Balance Model ◽

Dependent Manner ◽

Loss Of Function ◽

Concentration Dependent Manner ◽

Shh Pathway ◽

Embryonic Morphogenesis ◽

Malformation Syndromes ◽

Molecular Bases

Human hereditary malformation syndromes are caused by mutations in the genes of the signal transduction molecules involved in fetal development. Among them, the Sonic hedgehog (SHH) signaling pathway is the most important, and many syndromes result from its disruption. In this review, we summarize the molecular mechanisms and role in embryonic morphogenesis of the SHH pathway, then classify the phenotype of each malformation syndrome associated with mutations of major molecules in the pathway. The output of the SHH pathway is shown as GLI activity, which is generated by SHH in a concentration-dependent manner, i.e., the sum of activating form of GLI (GLIA) and repressive form of GLI (GLIR). Which gene is mutated and whether the mutation is loss-of-function or gain-of-function determine in which concentration range of SHH the imbalance occurs. In human malformation syndromes, too much or too little GLI activity produces symmetric phenotypes affecting brain size, craniofacial (midface) dysmorphism, and orientation of polydactyly with respect to the axis of the limb. The symptoms of each syndrome can be explained by the GLIA/R balance model.

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The CUP-SHAPED COTYLEDON1 gene of Arabidopsis regulates shoot apical meristem formation

Development ◽

10.1242/dev.128.7.1127 ◽

2001 ◽

Vol 128 (7) ◽

pp. 1127-1135 ◽

Cited By ~ 6

Author(s):

S. Takada ◽

K. Hibara ◽

T. Ishida ◽

M. Tasaka

Keyword(s):

Shoot Apical Meristem ◽

Apical Meristem ◽

Molecular Mechanisms ◽

Higher Plants ◽

Adventitious Shoots ◽

Floral Organ ◽

Loss Of Function ◽

Nac Domain ◽

Redundant Genes ◽

Domain Protein

In higher plants, molecular mechanisms regulating shoot apical meristem (SAM) formation and organ separation are largely unknown. The CUC1 (CUP-SHAPED COTYLEDON1) and CUC2 are functionally redundant genes that are involved in these processes. We cloned the CUC1 gene by a map-based approach, and found that it encodes a NAC-domain protein highly homologous to CUC2. CUC1 mRNA was detected in the presumptive SAM during embryogenesis, and at the boundaries between floral organ primordia. Surprisingly, overexpression of CUC1 was sufficient to induce adventitious shoots on the adaxial surface of cotyledons. Expression analyses in the overexpressor and in loss-of-function mutants suggest that CUC1 acts upstream of the SHOOT MERISTEMLESS gene.

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c-Jun NH2-terminal Kinase (JNK)-interacting Protein-3 (JIP3) Regulates Neuronal Axon Elongation in a Kinesin- and JNK-dependent Manner

Journal of Biological Chemistry ◽

10.1074/jbc.m113.464453 ◽

2013 ◽

Vol 288 (20) ◽

pp. 14531-14543 ◽

Cited By ~ 36

Author(s):

Tao Sun ◽

Nuo Yu ◽

Lu-Kai Zhai ◽

Na Li ◽

Chao Zhang ◽

...

Keyword(s):

Cortical Neurons ◽

Hippocampal Neurons ◽

Molecular Mechanisms ◽

Neuronal Development ◽

Dependent Manner ◽

Loss Of Function ◽

Anterograde Transport ◽

Interacting Protein ◽

Axon Elongation

The development of neuronal polarity is essential for the establishment of the accurate patterning of neuronal circuits in the brain. However, little is known about the underlying molecular mechanisms that control rapid axon elongation during neuronal development. Here, we report that c-Jun NH2-terminal kinase (JNK)-interacting protein-3 (JIP3) is highly expressed at axon tips during the critical period for axon development. Using gain- and loss-of-function approaches, immunofluorescence analysis, and in utero electroporation, we find that JIP3 can enhance axon elongation in primary hippocampal neurons and cortical neurons in vivo. We further demonstrate that JIP3 promotes axon elongation in a kinesin- and JNK-dependent manner using several deletion mutants of JIP3. Next, we demonstrate that the successful transportation of JIP3 to axon tips by kinesin is a prerequisite for enhancing JNK phosphorylation in this area and therefore promotes axon elongation, constituting a novel mechanism for coupling JIP3 anterograde transport with JNK signaling at the distal axons and axon elongation. Finally, our immunofluorescence data suggest that the activation of JNK at axon tips facilitates axon elongation by modulating cofilin activity and actin filament dynamics. These findings may have important implications for our understanding of neuronal axon elongation during development.

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Nogo-A Modulates the Synaptic Excitation of Hippocampal Neurons in a Ca2+-Dependent Manner

Cells ◽

10.3390/cells10092299 ◽

2021 ◽

Vol 10 (9) ◽

pp. 2299

Author(s):

Kristin Metzdorf ◽

Steffen Fricke ◽

Maria Teresa Balia ◽

Martin Korte ◽

Marta Zagrebelsky

Keyword(s):

Synaptic Plasticity ◽

Hippocampal Neurons ◽

Molecular Mechanisms ◽

Growth Inhibitor ◽

Neurite Growth ◽

Excitatory Synapses ◽

Dependent Manner ◽

Loss Of Function ◽

Synaptic Excitation ◽

Primary Mouse

A tight regulation of the balance between inhibitory and excitatory synaptic transmission is a prerequisite for synaptic plasticity in neuronal networks. In this context, the neurite growth inhibitor membrane protein Nogo-A modulates synaptic plasticity, strength, and neurotransmitter receptor dynamics. However, the molecular mechanisms underlying these actions are unknown. We show that Nogo-A loss-of-function in primary mouse hippocampal cultures by application of a function-blocking antibody leads to higher excitation following a decrease in GABAARs at inhibitory and an increase in the GluA1, but not GluA2 AMPAR subunit at excitatory synapses. This unbalanced regulation of AMPAR subunits results in the incorporation of Ca2+-permeable GluA2-lacking AMPARs and increased intracellular Ca2+ levels due to a higher Ca2+ influx without affecting its release from the internal stores. Increased neuronal activation upon Nogo-A loss-of-function prompts the phosphorylation of the transcription factor CREB and the expression of c-Fos. These results contribute to the understanding of the molecular mechanisms underlying the regulation of the excitation/inhibition balance and thereby of plasticity in the brain.

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Cylindromatosis Drives Synapse Pruning and Weakening by Promoting Macroautophagy through Akt-mTOR Signaling

10.1101/2021.12.08.471792 ◽

2021 ◽

Author(s):

Wei-Dong Yao ◽

Alexis S Zajicek ◽

Huihui Dai ◽

Mary Catherine Skolfield ◽

Hannah L Phillips ◽

...

Keyword(s):

Molecular Mechanisms ◽

Mtor Signaling ◽

Mammalian Brain ◽

Autophagic Flux ◽

Dependent Manner ◽

Synapse Elimination ◽

Loss Of Function ◽

Synapse Maintenance ◽

Behavioral Impairments

The lysine-63 deubiquitinase cylindromatosis (CYLD) is long recognized as a tumor suppressor in immunity and inflammation and its loss-of-function mutations lead to familial cylindromatosis. However, recent studies reveal that CYLD is enriched in mammalian brain postsynaptic densities, and a gain-of-function mutation causes frontotemporal dementia (FTD), suggesting critical roles at excitatory synapses. Here we report that CYLD drives synapse elimination and weakening by acting on the Akt-mTOR-autophagy axis. Mice lacking CYLD display abnormal sociability, anxiety- and depression-like behaviors, and cognitive inflexibility. These behavioral impairments are accompanied by excessive synapse numbers, increased postsynaptic efficacy, augmented synaptic summation, and impaired NMDA receptor-dependent hippocampal long-term depression (LTD). Exogenous expression of CYLD results in removal of established dendritic spines from mature neurons in a deubiquitinase activity-dependent manner. In search of underlying molecular mechanisms, we find that CYLD knockout mice display marked overactivation of Akt and mTOR and reduced autophagic flux and, conversely, CYLD overexpression potently suppresses Akt and mTOR activity and promotes autophagy. Consequently, abrogating the Akt-mTOR-autophagy signaling pathway abolishes CYLD-induced spine loss, whereas enhancing autophagy in vivo by the mTOR inhibitor rapamycin rescues the synaptic pruning and LTD deficits in mutant mice. Our findings establish CYLD, via Akt-mTOR signaling, as a synaptic autophagy activator that exerts critical modulations on synapse maintenance, function, and plasticity.

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A balance of FGF and BMP signals regulates cell cycle exit and Equarin expression in lens cells

Molecular Biology of the Cell ◽

10.1091/mbc.e12-01-0075 ◽

2012 ◽

Vol 23 (16) ◽

pp. 3266-3274 ◽

Cited By ~ 24

Author(s):

Miguel Jarrin ◽

Tanushree Pandit ◽

Lena Gunhaga

Keyword(s):

Cell Cycle ◽

Molecular Mechanisms ◽

Dependent Manner ◽

Lens Fiber ◽

Cell Cycle Exit ◽

Loss Of Function ◽

Fiber Cells ◽

Morphogenetic Protein ◽

Lens Cells ◽

Chick Lens

In embryonic and adult lenses, a balance of cell proliferation, cell cycle exit, and differentiation is necessary to maintain physical function. The molecular mechanisms regulating the transition of proliferating lens epithelial cells to differentiated primary lens fiber cells are poorly characterized. To investigate this question, we used gain- and loss-of-function analyses to modulate fibroblast growth factor (FGF) and/or bone morphogenetic protein (BMP) signals in chick lens/retina explants. Here we show that FGF activity plays a key role for proliferation independent of BMP signals. Moreover, a balance of FGF and BMP signals regulates cell cycle exit and the expression of Ccdc80 (also called Equarin), which is expressed at sites where differentiation of lens fiber cells occurs. BMP activity promotes cell cycle exit and induces Equarin expression in an FGF-dependent manner. In contrast, FGF activity is required but not sufficient to induce cell cycle exit or Equarin expression. Furthermore, our results show that in the absence of BMP activity, lens cells have increased cell cycle length or are arrested in the cell cycle, which leads to decreased cell cycle exit. Taken together, these findings suggest that proliferation, cell cycle exit, and early differentiation of primary lens fiber cells are regulated by counterbalancing BMP and FGF signals.

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A screen for suppressors of apoptosis identifies a novel gain of function mutation in drosphilia RAS1s

Clinical & Investigative Medicine ◽

10.25011/cim.v30i4.2853 ◽

2007 ◽

Vol 30 (4) ◽

pp. 82

Author(s):

C Gafuik ◽

J Agapite ◽

H Steller

Keyword(s):

Cell Death ◽

Molecular Mechanisms ◽

Mapk Pathway ◽

Model Organisms ◽

Dependent Manner ◽

Loss Of Function ◽

Gain Of Function ◽

Ras Oncogenes ◽

Induced Apoptosis

Background: Apoptosis is a morphologically distinct, genetically programmed form of cell death that is evolutionarily highly conserved amongst multi-cellular eukaryotes. Correct regulation of apoptosis is critical for normal development and the prevention of diseases, such as cancer. Genetic analysis of invertebrate model organisms has proven invaluable for the identification and study of key molecules involved in apoptosis. In Drosophila, the proteins Reaper (Rpr), Head involution defective (Hid) and Grim induce cell death in a caspase dependent manner by inhibiting the anti-apoptotic function of diap1. Methods: To further elucidate the molecular mechanisms underlying the control of apoptosis, we conducted a dominant modifier screen for genes that could suppress the strong eye ablation phenotype caused by expressing hid under the control of an eye-specific promoter. Results: As previously reported, we identified several loss of function mutants in components of the EGFR/Ras/MAPK pathway that could dominantly suppress hid-induced apoptosis. These mutants proved to be alleles of either sprouty or gap1, two negative regulators of the RTK/Ras1 signaling. Here we report the identification and characterization of the first gain of function mutation in the Drosophila RAS1 gene. Conclusions: Taken together, these findings provide a molecular paradigm for the anti-apoptotic function of ras oncogenes.

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PINK1 import regulation at a crossroad of mitochondrial fate: the molecular mechanisms of PINK1 import

The Journal of Biochemistry ◽

10.1093/jb/mvz069 ◽

2019 ◽

Cited By ~ 2

Author(s):

Shiori Sekine

Keyword(s):

Health Status ◽

Ubiquitin Ligase ◽

Molecular Mechanisms ◽

Mitochondrial Damage ◽

Dependent Manner ◽

Loss Of Function ◽

Kinase Activation ◽

Critical Step ◽

Signalling Cascades ◽

Stress Dependent

Abstract PTEN-induced kinase 1 (PINK1) is a mitochondrial kinase whose activity is tightly regulated by the mitochondrial health status. In response to mitochondrial damage, activated PINK1 can promote mitophagy, an autophagic elimination of damaged mitochondria, by cooperating with Parkin ubiquitin ligase. Loss-of-function of PINK1/Parkin-mediated mitophagy results in the accumulation of dysfunctional mitochondria, which could be one aetiology of Parkinson’s disease (PD). Within step-by-step signalling cascades of PINK1/Parkin-mediated mitophagy, mitochondrial damage-dependent PINK1 kinase activation is a critical step to trigger the mitophagy signal. Recent investigation of this process reveals that this stress-dependent PINK1 kinase activation is achieved by its regulated import into different mitochondrial compartments. Thus, PINK1 import regulation stands at an important crossroad to determine the mitochondrial fate—‘keep’ or ‘remove’? In this review, we will summarize how the PINK1 import is regulated in a mitochondrial health status-dependent manner and how this process could be pharmacologically modulated to activate the PINK1/Parkin pathway.

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Loss of Function of von Hippel-Lindau Trigger Lipocalin 2-Dependent Inflammatory Responses in Cultured and Primary Renal Tubular Cells

Oxidative Medicine and Cellular Longevity ◽

10.1155/2021/5571638 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Chan-Yen Kuo ◽

Valeria Chiu ◽

Po-Chun Hsieh ◽

Tien Hsu ◽

Ting-Yun Lin

Keyword(s):

Molecular Mechanisms ◽

Inflammatory Responses ◽

Conditional Knockout ◽

Dependent Manner ◽

Lipocalin 2 ◽

Loss Of Function ◽

Von Hippel Lindau ◽

Tubular Cells ◽

Renal Tubular Cells ◽

Renal Tubular

Previous studies have shown that mutations in the tumor suppressor gene von Hippel-Lindau (VHL) can result in the overproduction of reactive oxygen species (ROS) and chronic inflammation and are a significant predisposing factor for the development of clear-cell renal cell carcinoma (ccRCC). To study VHL’s role in ccRCC formation, we previously developed a novel conditional knockout mouse model that mimicked the features of kidney inflammation and fibrosis that lead to cyst formation and hyperplasia. However, due to VHL’s complex cellular functions, the mechanism of this phenomenon remains unclear. Here, we used the HK-2 cells and mouse primary renal tubule cells (mRTCs) carrying VHL mutations as models to study the effects and underlying molecular mechanisms of ROS accumulation. We also studied the role of lipocalin 2 (LCN2) in regulating macrophage recruitment by HK-2 cells. We measured the level of ROS in HK-2 cells in the presence or absence of LCN2 knockdown and found that the VHL mutation caused ROS overproduction, but an LCN2 knockdown could attenuate the process. VHL was also found to mediate the in vitro and in vivo expression and secretion of LCN2. Thus, VHL likely affects ROS production in an LCN2-dependent manner. Our findings also suggest that LCN2 sensitizes the inflammatory response of HK-2 cells and the chemotactic abilities of macrophage RAW264.7 cells. By demonstrating that the loss of function of von Hippel-Lindau triggers lipocalin 2-dependent inflammatory responses in cultured and primary renal tubular cells, our results offer novel insights into a potential therapeutic approach for interfering with the development of ccRCC.

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The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000195 ◽

2014 ◽

Vol 84 (1-2) ◽

pp. 79-91 ◽

Cited By ~ 7

Author(s):

Amin F. Majdalawieh ◽

Hyo-Sung Ro

Keyword(s):

Cholesterol Efflux ◽

Transcriptional Activity ◽

Molecular Mechanisms ◽

Foam Cell ◽

Mapk Signaling ◽

Luciferase Reporter ◽

Foam Cell Formation ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamins anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

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