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Nature Nov 2015Piezo proteins are evolutionarily conserved and functionally diverse mechanosensitive cation channels. However, the overall structural architecture and gating mechanisms...
Piezo proteins are evolutionarily conserved and functionally diverse mechanosensitive cation channels. However, the overall structural architecture and gating mechanisms of Piezo channels have remained unknown. Here we determine the cryo-electron microscopy structure of the full-length (2,547 amino acids) mouse Piezo1 (Piezo1) at a resolution of 4.8 Å. Piezo1 forms a trimeric propeller-like structure (about 900 kilodalton), with the extracellular domains resembling three distal blades and a central cap. The transmembrane region has 14 apparently resolved segments per subunit. These segments form three peripheral wings and a central pore module that encloses a potential ion-conducting pore. The rather flexible extracellular blade domains are connected to the central intracellular domain by three long beam-like structures. This trimeric architecture suggests that Piezo1 may use its peripheral regions as force sensors to gate the central ion-conducting pore.
Topics: Animals; Cell Membrane; Cryoelectron Microscopy; Electric Conductivity; Ion Channel Gating; Ion Channels; Mice; Models, Molecular; Pliability; Protein Multimerization; Protein Structure, Quaternary; Protein Structure, Tertiary; Protein Subunits
PubMed: 26390154
DOI: 10.1038/nature15247 -
Current Opinion in Structural Biology Feb 2019Ionotropic glutamate receptors in vertebrates are composed of three major subtypes - AMPA, kainate, and NMDA receptors - and mediate the majority of fast excitatory... (Review)
Review
Ionotropic glutamate receptors in vertebrates are composed of three major subtypes - AMPA, kainate, and NMDA receptors - and mediate the majority of fast excitatory neurotransmission at chemical synapses of the central nervous system. Among the three major families, native AMPA receptors function as complexes with a variety of auxiliary subunits, which in turn modulate receptor trafficking, gating, pharmacology, and permeation. Despite the long history of structure-mechanism studies using soluble receptor domains or intact yet isolated receptors, structures of AMPA receptor-auxiliary subunit complexes have not been available until recent breakthroughs in single-particle cryo-electron microscopy. Single particle cryo-EM studies have, in turn, provided new insights into the structure and organization of AMPA receptor - auxiliary protein complexes and into the molecular mechanisms of AMPA receptor activation and desensitization.
Topics: Animals; Protein Subunits; Receptors, AMPA
PubMed: 30825796
DOI: 10.1016/j.sbi.2019.01.011 -
Hypertension (Dallas, Tex. : 1979) Jun 2023Vascular smooth muscle cell (VSMC) contractility is critical for blood pressure regulation and vascular homeostasis. Identifying the key molecule that maintains VSMC...
Activin Receptor-Like Kinase 3 Directly Couples Gαq (Guanine Nucleotide-Binding Protein Subunit αq)/ Gαq (Guanine Nucleotide-Binding Protein Subunit α11) to Regulate Vascular Contractility.
BACKGROUND
Vascular smooth muscle cell (VSMC) contractility is critical for blood pressure regulation and vascular homeostasis. Identifying the key molecule that maintains VSMC contractility may provide a novel therapeutic target for vascular remodeling. ALK3 (activin receptor-like kinase 3) is a serine/threonine kinase receptor, and deletion of ALK3 causes embryonic lethality. However, little is known about the role of ALK3 in postnatal arterial function and homeostasis.
METHODS
We conducted in vivo studies in a tamoxifen-induced postnatal VSMC-specific ALK3 deletion mice suitable for analysis of blood pressure and vascular contractility. Additionally, the role of ALK3 on VSMC was determined using Western blot, collagen-based contraction assay and traction force microscopy. Furthermore, interactome analysis were performed to identify the ALK3-associated proteins and bioluminescence resonance energy transfer assay was used to characterize Gαq activation.
RESULTS
ALK3 deficiency in VSMC led to spontaneous hypotension and impaired response to angiotensin II in mice. In vivo and in vitro data revealed that ALK3 deficiency impaired contraction force generation by VSMCs, repressed the expression of contractile proteins, and inhibited the phosphorylation of myosin light chain. Mechanistically, Smad1/5/8 signaling mediated the ALK3-modulated contractile protein expressions but not myosin light chain phosphorylation. Furthermore, interactome analysis revealed that ALK3 directly interacted with and activated Gαq (guanine nucleotide-binding protein subunit αq)/Gα11 (guanine nucleotide-binding protein subunit α11), thereby stimulating myosin light chain phosphorylation and VSMC contraction.
CONCLUSIONS
Our study revealed that in addition to canonical Smad1/5/8 signaling, ALK3 modulates VSMC contractility through direct interaction with Gαq/Gα11, and therefore, might serve as a potential target for modulating aortic wall homeostasis.
Topics: Mice; Animals; Protein Subunits; Muscle, Smooth, Vascular; Bone Morphogenetic Protein Receptors, Type I; Blood Pressure; GTP-Binding Proteins; Myocytes, Smooth Muscle; Guanine Nucleotides; Cells, Cultured
PubMed: 36999441
DOI: 10.1161/HYPERTENSIONAHA.122.20654 -
BMB Reports Sep 2016Neurodegenerative diseases (NDs) often involve the formation of abnormal and toxic protein aggregates, which are thought to be the primary factor in ND occurrence and... (Review)
Review
Neurodegenerative diseases (NDs) often involve the formation of abnormal and toxic protein aggregates, which are thought to be the primary factor in ND occurrence and progression. Aged neurons exhibit marked increases in aggregated protein levels, which can lead to increased cell death in specific brain regions. As no specific drugs/therapies for treating the symptoms or/and progression of NDs are available, obtaining a complete understanding of the mechanism underlying the formation of protein aggregates is needed for designing a novel and efficient removal strategy. Intracellular proteolysis generally involves either the lysosomal or ubiquitin-proteasome system. In this review, we focus on the structure and assembly of the proteasome, proteasome-mediated protein degradation, and the multiple dynamic regulatory mechanisms governing proteasome activity. We also discuss the plausibility of the correlation between changes in proteasome activity and the occurrence of NDs. [BMB Reports 2016; 49(9): 459-473].
Topics: Archaea; Humans; Neurodegenerative Diseases; Phosphorylation; Proteasome Endopeptidase Complex; Protein Subunits; Sumoylation; Ubiquitination
PubMed: 27312603
DOI: 10.5483/bmbrep.2016.49.9.094 -
The Biochemical Journal Nov 2018Heterotrimeric G proteins composed of Gα, Gβ, and Gγ subunits are vital eukaryotic signaling elements that convey information from ligand-regulated G protein-coupled... (Review)
Review
Heterotrimeric G proteins composed of Gα, Gβ, and Gγ subunits are vital eukaryotic signaling elements that convey information from ligand-regulated G protein-coupled receptors (GPCRs) to cellular effectors. Heterotrimeric G protein-based signaling pathways are fundamental to human health [ (2007) , 994-1005] and are the target of >30% of pharmaceuticals in clinical use [ (2013) , 1676-1694; (2017) , 829-842]. This review focuses on phosphorylation of G protein subunits as a regulatory mechanism in mammals, budding yeast, and plants. This is a re-emerging field, as evidence for phosphoregulation of mammalian G protein subunits from biochemical studies in the early 1990s can now be complemented with contemporary phosphoproteomics and genetic approaches applied to a diversity of model systems. In addition, new evidence implicates a family of plant kinases, the receptor-like kinases, which are monophyletic with the interleukin-1 receptor-associated kinase/Pelle kinases of metazoans, as possible GPCRs that signal via subunit phosphorylation. We describe early and modern observations on G protein subunit phosphorylation and its functional consequences in these three classes of organisms, and suggest future research directions.
Topics: Animals; Heterotrimeric GTP-Binding Proteins; Humans; Mammals; Phosphorylation; Plants; Protein Binding; Protein Subunits; Saccharomyces cerevisiae; Signal Transduction
PubMed: 30413679
DOI: 10.1042/BCJ20160819 -
Current Molecular Pharmacology 2015Due to their essential biological roles, voltage-gated calcium channels (VGCCs) are regulated by a myriad of molecules and mechanisms. Fifteen years ago, RGK proteins... (Review)
Review
Due to their essential biological roles, voltage-gated calcium channels (VGCCs) are regulated by a myriad of molecules and mechanisms. Fifteen years ago, RGK proteins were discovered to bind the VGCC β subunit (Cavβ) and potently inhibit high-voltage activated Ca(2+) channels. RGKs (Rad, Rem, Rem2 and Gem/Kir) are a family of monomeric small GTPases belonging to the superfamily of Ras GTPases. They exert dual inhibitory effects on VGCCs, decreasing surface expression and suppressing surface channels through immobilization of the voltage sensor or reduction of channel open probability. While Cavβ is required for all forms of RGK inhibition, not all inhibition is mediated by the RGK-Cavβ interaction. Some RGK proteins also interact directly with the pore-forming α1 subunit of some types of VGCCs (Cavα1). Importantly, RGK proteins tonically inhibit VGCCs in native cells, regulating cardiac and neural functions. This minireview summarizes the mechanisms, molecular determinants, and physiological impact of RGK inhibition of VGCCs.
Topics: Animals; Calcium Channels; Humans; Ion Channel Gating; Models, Biological; Models, Molecular; Monomeric GTP-Binding Proteins; Protein Binding; Protein Structure, Tertiary; Protein Subunits
PubMed: 25966691
DOI: 10.2174/1874467208666150507105613 -
Advances in Experimental Medicine and... 2016Two-dimensional nanoscale assemblies (nanosheets) represent a promising structural platform to arrange molecular and supramolecular substrates with precision for... (Review)
Review
Two-dimensional nanoscale assemblies (nanosheets) represent a promising structural platform to arrange molecular and supramolecular substrates with precision for integration into devices. This nanoarchitectonic approach has gained significant traction over the last decade, as a general concept to guide the fabrication of functional nanoscale devices. Sequence-specific biomolecules, e.g., peptides and proteins, may be considered excellent substrates for the fabrication of two-dimensional nanoarchitectonics. Molecular level instructions can be encoded within the sequence of monomers, which allows for control over supramolecular structure if suitable design principles could be elaborated. Due to the complexity of interactions between protomers, the development of principles aimed toward rational design of peptide and protein nanosheets is at a nascent stage. This review discusses the known two-dimensional peptide and protein assemblies to further our understanding of how to control the arrangement of molecules in two-dimensions.
Topics: Nanostructures; Peptides; Protein Engineering; Protein Subunits
PubMed: 27677508
DOI: 10.1007/978-3-319-39196-0_3 -
Proceedings of the National Academy of... Aug 2023Cells of vertebrate and invertebrate organisms express proteins specialized in membrane channel-based cell-cell communication that are absent in unicellular organisms....
Cells of vertebrate and invertebrate organisms express proteins specialized in membrane channel-based cell-cell communication that are absent in unicellular organisms. We recently described the prediction of some members of the large-pore channel family in kinetoplastids, consisting of proteins called unnexins, which share several structural features with innexin and pannexin proteins. Here, we demonstrated that the unnexin1 protein (Unx1) is delivered to the cell membrane, displaying a topology consisting of four transmembrane domains with C and N termini on the cytoplasmic side and form large-pore channels that are permeable to small molecules. Low extracellular Ca/Mg levels or extracellular alkalinization, but not mechanical stretching, increases channel activity. The Unx1 channel mediates the influx of Ca and does not form intercellular dye coupling between HeLa Unx1 transfected cells. Unx1 channel function was further evidenced by its ability to mediate ionic currents when expressed in oocytes. Downregulation of Unx1 mRNA with morpholine contains invasion. Phylogenetic analysis revealed the presence of Unx1 homologs in other protozoan parasites, suggesting a conserved function for these channel parasites in other protists. Our data demonstrate that Unx1 forms large-pore membrane channels, which may serve as a diffusional pathway for ions and small molecules that are likely to be metabolic substrates or waste products, and signaling autocrine and paracrine molecules that could be involved in cell invasion. As morpholinos-induced downregulation of Unx1 reduces the infectivity of trypomastigotes, the Unx1 channels might be an attractive target for developing trypanocide drugs.
Topics: Protein Subunits; Phylogeny; Cell Membrane; Cytoplasm; Morpholinos
PubMed: 37487087
DOI: 10.1073/pnas.2307898120 -
PloS One 2023Most proteins form complexes consisting of two or more subunits, where complex assembly can proceed via two competing pathways: co-translational assembly of a mature and...
Most proteins form complexes consisting of two or more subunits, where complex assembly can proceed via two competing pathways: co-translational assembly of a mature and a nascent subunit, and post-translational assembly by two mature protein subunits. Assembly pathway dominance, i.e., which of the two pathways is predominant under which conditions, is poorly understood. Here, we introduce a reaction-diffusion system that describes protein complex formation via post- and co-translational assembly and use it to analyze the dominance of both pathways. Special features of this new system are (i) spatially inhomogeneous sources of reacting species, (ii) a combination of diffusing and immobile species, and (iii) an asymmetric binding competition between the species. We study assembly pathway dominance for the spatially homogeneous system and find that the ratio of production rates of the two protein subunits determines the long-term pathway dominance. This result is independent of the binding rate constants for post- and co-translational assembly and implies that a system with an initial post-translational assembly dominance can eventually exhibit co-translational assembly dominance and vice versa. For exactly balanced production of both subunits, the assembly pathway dominance is determined by the steady state concentration of the subunit that can bind both nascent and mature partners. The introduced system of equations can be applied to describe general dynamics of assembly processes involving both diffusing and immobile components.
Topics: Protein Subunits; Protein Biosynthesis
PubMed: 36827413
DOI: 10.1371/journal.pone.0281964 -
International Journal of Molecular... Oct 2021As the central node between nutrition signaling input and the metabolic pathway, AMP-activated protein kinase (AMPK) is tightly regulated to maintain energy homeostasis.... (Review)
Review
As the central node between nutrition signaling input and the metabolic pathway, AMP-activated protein kinase (AMPK) is tightly regulated to maintain energy homeostasis. Subcellular compartmentalization of AMPK is one of the critical regulations that enables AMPK to access proper targets and generate appropriate responses to specific perturbations and different levels of stress. One of the characterized localization mechanisms is RanGTPase-driven CRM1 that recognizes the nuclear export sequence (NES) on the α subunit to translocate AMPK into the cytoplasm. Nuclear localization putatively employs RanGTPase-driven importin that might recognize the nuclear localization signal (NLS) present on the AMPKα2 kinase domain. Nucleo-cytoplasmic shuttling of AMPK is influenced by multiple factors, such as starvation, exercise, heat shock, oxidant, cell density, and circadian rhythm. Tissue-specific localization, which distributes AMPK trimers with different combinations, has also been shown to be vital in maintaining tissue-specific metabolism. Tissue-specific and subcellular distribution of AMPK might be attributed to differences in the expression of the subunit, the stabilization by protein regulators, tissue activity, and the localization of AMPK activators. Considering the importance of AMPK localization in coordinating signaling and metabolism, further research is due to fully elucidate the largely unknown complex mechanism underlying this regulation.
Topics: AMP-Activated Protein Kinases; Active Transport, Cell Nucleus; Cell Nucleus; Circadian Rhythm; Cytoplasm; Energy Metabolism; Heat-Shock Response; Humans; Karyopherins; Protein Subunits; Receptors, Cytoplasmic and Nuclear; Exportin 1 Protein
PubMed: 34681581
DOI: 10.3390/ijms222010921