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Subneuronal Processing of Information by Solitary Waves and Stochastic Processes
Published in Sergey Edward Lyshevski, Nano and Molecular Electronics Handbook, 2018
Danko D. Georgiev, James F. Glazebrook
We proceed to describe two important mechanisms corresponding to protein constituents such as synapsin-1 and synaptotagmin-1. In [61], it is proposed that phosphorylation of synapsin-1 by Ca2+ dependent kinases, on releasing synaptic vesicles (SVs) from actin filaments, may accelerate the passage of vesicles to the presynaptic membrane. Thus, the Ca2+ entry may stimulate the engagement of SVs from the reserve pool making them tether and dock within the active zone where they are available for rapid release. In [62], it is shown that cytoskeletal protein tubulin binds directly to synaptotagmin-1, which promotes tubulin assembly. At the same time, synaptotagmin-1 functions by attaching synaptic vesicles to microtubules in high concentrations of Ca2+.
Advances of engineered extracellular vesicles-based therapeutics strategy
Published in Science and Technology of Advanced Materials, 2022
Hiroaki Komuro, Shakhlo Aminova, Katherine Lauro, Masako Harada
The first approach, the endogenous method, loads therapeutic drugs into EVs before EVs are isolation from producer cells. In endogenous loading, the encapsulated small molecule acting as cargo in the EV is loaded into vesicles during production by incubating it directly with the parent cells Protein and nucleic acids can also be loaded into EVs by transfection of the producer cell with the encoding DNA. There are various approaches to improving the loading efficiency of nucleic acids into EVs. One approach uses sequence motifs present in miRNAs to control their localization into EVs [149,150]. Certain proteins identified include heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) [149], synaptotagmin-binding cytoplasmic RNA-interacting protein (SYNCRIP) [151], Y-box protein 1 (YBX1) [152], which recognize these motifs and bind specifically to exosomal miRNAs and regulate their loading into EVs. Another approach fuses an interaction module with a membrane protein that acts as a marker for EVs and other types of EVs. The method of fusing a protein-binding domain or a sequence-specific nucleic acid-binding domain to tetraspanin (especially CD63, CD9, and CD81), Lamp2b, and a transferrin receptor is used to load any protein or nucleic acid [70,153]. For example, the method of fusing sequence-specific nucleic acid binding motifs such as MS2 [154], L7Ae [155], and Tat [156] to load nucleic acids has been reported. However, these systems are limited in their ability to release the cargo into the cytoplasm in target cells and require further optimization. Examples of this are the iDimerizeTM Inducible A/C heterodimer system [157,158], which induces ligand-dependent dimer, and the CRY2-CIB1 system [159], which can control protein interactions with specific wavelengths of light. Collectively, passive incubation in parent cells showed an encapsulation of various therapeutic drugs, which is simple and does not require any special equipment. However, due to the toxicity of EV-producing cells and the inefficient drug loading, there are limitations to its use in applications. Hence, bioinformatic analyses will be further needed to investigate more specific RNA sequencing binding proteins and EV-rich RNA sequencing.
The cationic (calcium and lead) and enzyme conundrum
Published in Journal of Toxicology and Environmental Health, Part B, 2018
Jane Kasten-Jolly, David A. Lawrence
The interplay of Pb and Ca first became noticed during studies concerning Pb effects on synaptic neuronal transmission. Kostial and Vouk (1957) observed that addition of Ca was able to reverse the inhibitory effect of Pb on cholinergic transmission in their cat nictitating membrane system. Various investigators suggested that Pb demonstrated the ability to substitute for Ca in intracellular regulatory mechanisms, which might form the basis for Pb’s neurotoxicity (Bressler, Forman, and Goldstein 1994; Bressler and Goldstein 1991; Goering 1993; Goldstein 1993; Marchetti 2003). Among the regulatory processes reviewed were activation of calmodulin-dependent phosphodiesterase, calmodulin inhibitor sensitive potassium channels, and calmodulin-independent PKC activity. Further, under the control of calmodulin are the Ca-calmodulin-dependent protein kinases (Soderling 1999; Swulius and Waxham 2008). With the advent of sensitive methods to measure intracellular Ca and Pb, such as 5F-BAPTA by NMR or the fluorescent indicator Fura-2, it became evident that Pb could promote an elevation in intracellular cytosolic free Ca (Simons 1993). Increases in cytoplasmic Ca concentration subsequently trigger a variety of cellular events depending on the type of cell involved. In erythrocytes, Pb inhibits the Ca pump (Ca-ATPase). Inhibition by Pb was even observed in the presence of calmodulin, which functions as an endogenous activator of the Ca pump. In erythrocytes, Pb also may substitute for Ca in Ca-dependent potassium (K) channels including the cells to leak K (Simons 1985); however, a Pb concentration of 25–30 μM was needed, which is an amount too high to be relevant for environmental Pb toxicity of humans. With respect to neuronal cells, Pb might block Ca entry through Ca channels. Pb within the nerve terminals may either stimulate basal secretion of the transmitter, or promote spontaneous transmitter release (Goldstein 1993). The subject of Pb interactions with Ca binding proteins present in the central nervous system was recently reviewed (Gorkhali et al. 2016). Among the proteins discussed in this article were: calmodulin, synaptotagmin, neuronal calcium sensor-1 (NCS-1), N-methyl-D-aspartate receptor (NMDAR), and family C of G-protein coupled receptors (cGPCRs). Binding differences between Pb and Ca for calmodulin were assessed by means of NMR and fluorescence spectroscopy, and the results pointed to an opportunistic, allosteric binding to calmodulin that was distinct from ionic displacement (Kirberger et al. 2013). Taken together, information gleaned from studies of the interaction of Pb with Ca binding proteins can be described by these three points: i) Pb might occupy Ca binding sites and inhibit protein activity through structural modulation, ii) Pb may mimic Ca and falsely activate the protein, thus affecting downstream events, iii) Pb might bind outside of the Ca binding region and induce allosteric modulation of protein activity. With respect to some Ca binding proteins, Pb at low concentrations, pM – nM, might activate activity, but Pb at higher concentrations, μM, produce inhibition of the protein’s activity.