scholarly journals Calcium current modulation by the γ1 subunit depends on alternative splicing of CaV1.1

2021 ◽  
Author(s):  
Yousra El El Ghaleb ◽  
Nadine J. Ortner ◽  
Wilfried Posch ◽  
Monica L. Fernandez-Quintero ◽  
Wietske E. Tuinte ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Current Density ◽  
Voltage Dependence ◽  
Splice Variants ◽  
Calcium Currents ◽  
Developmentally Regulated ◽  
The Difference ◽  
Ion Conducting ◽  
And Shifts ◽  
Oppositely Charged

The skeletal muscle voltage-gated calcium channel (CaV1.1) primarily functions as voltage sensor for excitation-contraction coupling. Conversely, its ion-conducting function is modulated by multiple mechanisms within the pore-forming α1S subunit and the auxiliary α2δ-1 and γ1 subunits. Particularly, developmentally regulated alternative splicing of exon 29, which inserts 19 amino acids in the extracellular IVS3-S4 loop of CaV1.1a, greatly reduces the current density and shifts the voltage-dependence of activation to positive potentials outside the physiological range. We generated a new HEK293-cell line stably expressing α2δ-1, β3, and STAC3. When the adult (CaV1.1a) and the embryonic (CaV1.1e) splice variants were expressed in these cells, the difference in the voltage-dependence of activation observed in muscle cells was reproduced, but not the reduced current density of CaV1.1a. Only when we further co-expressed the γ1 subunit, the current density of CaV1.1a, but not of CaV1.1e, was reduced by >50 %. In addition, γ1 caused a shift of the voltage-dependence of inactivation to negative voltages in both variants. Thus, the current-reducing effect of γ1, but not its effect on inactivation, is specifically dependent on the inclusion of exon 29 in CaV1.1a. Molecular structure modeling revealed several direct ionic interactions between oppositely charged residues in the IVS3-S4 loop and the γ1 subunit. However, substitution of these residues by alanine, individually or in combination, did not abolish the γ1-dependent reduction of current density, suggesting that structural rearrangements of CaV1.1a induced by inclusion of exon 29 allosterically empower the γ1 subunit to exert its inhibitory action on CaV1.1 calcium currents.

scholarly journals Alternative Splicing Switches the Divalent Cation Selectivity of TRPM3 Channels

2005 ◽  
Vol 280 (23) ◽  
pp. 22540-22548 ◽  
Author(s):  
Johannes Oberwinkler ◽  
Annette Lis ◽  
Klaus M. Giehl ◽  
Veit Flockerzi ◽  
Stephan E. Philipp
Keyword(s):  
Alternative Splicing ◽  
Ion Channels ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Splice Variants ◽  
Large Family ◽  
Ionic Selectivity ◽  
Pore Region ◽  
Cation Selectivity ◽  
Ion Conducting

TRPM3 is a poorly understood member of the large family of transient receptor potential (TRP) ion channels. Here we describe five novel splice variants of TRPM3, TRPM3α1–5. These variants are characterized by a previously unknown amino terminus of 61 residues. The differences between the five variants arise through splice events at three different sites. One of these splice sites might be located in the pore region of the channel as indicated by sequence alignment with other, better-characterized TRP channels. We selected two splice variants, TRPM3α1 and TRPM3α2, that differ only in this presumed pore region and analyzed their biophysical characteristics after heterologous expression in human embryonic kidney 293 cells. TRPM3α1 as well as TRPM3α2 induced a novel, outwardly rectifying cationic conductance that was tightly regulated by intracellular Mg2+. However, these two variants are highly different in their ionic selectivity. Whereas TRPM3α1-encoded channels are poorly permeable for divalent cations, TRPM3α2-encoded channels are well permeated by Ca2+ and Mg2+. Additionally, we found that currents through TRPM3α2 are blocked by extracellular monovalent cations, whereas currents through TRPM3α1 are not. These differences unambiguously show that TRPM3 proteins constitute a pore-forming channel subunit and localize the position of the ion-conducting pore within the TRPM3 protein. Although the ionic selectivity of ion channels has traditionally been regarded as rather constant for a given channel-encoding gene, our results show that alternative splicing can be a mechanism to produce channels with very different selectivity profiles.

scholarly journals Tissue-specific and developmentally regulated alternative splicing in mouse skeletal muscle ryanodine receptor mRNA

1995 ◽  
Vol 305 (2) ◽  
pp. 373-378 ◽  
Author(s):  
A Futatsugi ◽  
G Kuwajima ◽  
K Mikoshiba
Keyword(s):  
Skeletal Muscle ◽  
Alternative Splicing ◽  
Ryanodine Receptor ◽  
Splice Variants ◽  
Amino Acid Sequences ◽  
Pcr Analysis ◽  
Developmentally Regulated ◽  
Tissue Specific ◽  
Mouse Skeletal Muscle ◽  
Splicing Patterns

The ryanodine receptor is a channel for Ca2+ release from intracellular stores. By PCR analysis, we identified two alternatively spliced regions in mRNA of the mouse skeletal muscle ryanodine receptor (sRyR). The splice variants were characterized by the presence or absence of 15 bp (ASI) and 18 bp (ASII) exons. The exclusion of these exons results in the absence of the regions corresponding to Ala3481-Gln3485 and Val3865-Asn3870, respectively, of rabbit sRyR; these amino acid sequences exist in the modulatory region, where sites for phosphorylation and binding of Ca2+, calmodulin and ATP are postulated to be. We also detected sRyR in brain and heart as well as in skeletal muscle, and the splicing patterns were found to be tissue-specific. Only the ASII-lacking isoform was detected in heart, whereas in other tissues the ASII-containing isoform was predominant. The splicing patterns were also found to change during development. In skeletal muscle, the ASI-containing isoform increased gradually from embryo to adult. The ASII-lacking isoform abruptly increased upon birth, but the ASII-containing isoform increased steadily afterwards. In cerebrum, the ratio of the ASII-containing isoform to the ASII-lacking one increased abruptly during embryonic days 14 and 18. These findings suggest that the alternative splicing of ASI and ASII, by affecting the modulatory region, generates functionally different sRyR isoforms in a tissue-specific and developmentally regulated manner.

scholarly journals Aerobic Exercise Induces Alternative Splicing of Neurexins in Frontal Cortex

2021 ◽  
Vol 6 (2) ◽  
pp. 48
Author(s):  
Elisa Innocenzi ◽  
Ida Cariati ◽  
Emanuela De Domenico ◽  
Erika Tiberi ◽  
Giovanna D’Arcangelo ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Aerobic Exercise ◽  
Frontal Cortex ◽  
Molecular Mechanisms ◽  
Splice Variants ◽  
Brain Regions ◽  
Synaptic Function ◽  
Molecular Changes ◽  
Beneficial Effects ◽  
The Impact

Aerobic exercise (AE) is known to produce beneficial effects on brain health by improving plasticity, connectivity, and cognitive functions, but the underlying molecular mechanisms are still limited. Neurexins (Nrxns) are a family of presynaptic cell adhesion molecules that are important in synapsis formation and maturation. In vertebrates, three-neurexin genes (NRXN1, NRXN2, and NRXN3) have been identified, each encoding for α and β neurexins, from two independent promoters. Moreover, each Nrxns gene (1–3) has several alternative exons and produces many splice variants that bind to a large variety of postsynaptic ligands, playing a role in trans-synaptic specification, strength, and plasticity. In this study, we investigated the impact of a continuous progressive (CP) AE program on alternative splicing (AS) of Nrxns on two brain regions: frontal cortex (FC) and hippocampus. We showed that exercise promoted Nrxns1–3 AS at splice site 4 (SS4) both in α and β isoforms, inducing a switch from exon-excluded isoforms (SS4−) to exon-included isoforms (SS4+) in FC but not in hippocampus. Additionally, we showed that the same AE program enhanced the expression level of other genes correlated with synaptic function and plasticity only in FC. Altogether, our findings demonstrated the positive effect of CP AE on FC in inducing molecular changes underlying synaptic plasticity and suggested that FC is possibly a more sensitive structure than hippocampus to show molecular changes.

scholarly journals Inheritance and reflection: “re-study” of three anthropology fieldwork sites in China’s Yunnan Province

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Mingming Wang
Keyword(s):  
Rural Society ◽  
Research Report ◽  
Ancestor Worship ◽  
Land System ◽  
Peking University ◽  
The Difference ◽  
And Shifts ◽  
West Town ◽  
The Relationship

AbstractThis article is a research report involving three anthropological studies conducted during the period of “Kuige” and their “re-studies.” By narrating the project, I set forth my views on the connections and differences between Chinese anthropological explorations from two historical periods. These anthropological explorations refer to the study of Lu Village conducted by Fei Xiaotong, that of “West Town” (Xizhou) by Francis L. K. Hsu, and that of “Pai-IPai” (Dai) villages by Tien Ju-Kang. They were all completed in the late 1930s and early 1940s. Each writer extracted a framework to analyze the land system, ancestor worship, and the relationship between humans and gods from the writer’s own field experience. Despite the difference in research methods, all three studies noticed the cultural differences between rural society and modernity. Since 2000, Peking University and Yunnan Minzu University have launched a “Province-university Cooperation Project.” During the project, a research team formed of several young scholars revisited Lu Village, “West Town” (Xizhou), and Namu Village. These writers’ works were based on the data acquired in their fieldwork and drew upon the opinions raised by global anthropologists on “re-study” in recent decades. Considering the dual effects of social change and shifts in academic concepts around “follow-up research,” the scholars put forward several points of view with their ethnographies, which all featured the characteristics of inheritance and reflection. Based on the results of the three “re-studies,” this article emphasizes the importance of the study of public rituals for the research of rural society. This article also attempts to re-examine the methodology of “human ecology,” which profoundly impacts Chinese anthropology and sociology.

scholarly journals Regulation of Multiple Core Spliceosomal Proteins by Alternative Splicing-Coupled Nonsense-Mediated mRNA Decay

2008 ◽  
Vol 28 (13) ◽  
pp. 4320-4330 ◽  
Author(s):  
Arneet L. Saltzman ◽  
Yoon Ki Kim ◽  
Qun Pan ◽  
Matthew M. Fagnani ◽  
Lynne E. Maquat ◽  
...  
Keyword(s):  
Gene Expression ◽  
Alternative Splicing ◽  
Mrna Decay ◽  
Splice Variants ◽  
Cellular Functions ◽  
Regulate Gene Expression ◽  
Premature Termination Codons ◽  
Microarray Profiling ◽  
Nonsense Mediated Mrna Decay ◽  
Regulate Gene

ABSTRACT Alternative splicing (AS) can regulate gene expression by introducing premature termination codons (PTCs) into spliced mRNA that subsequently elicit transcript degradation by the nonsense-mediated mRNA decay (NMD) pathway. However, the range of cellular functions controlled by this process and the factors required are poorly understood. By quantitative AS microarray profiling, we find that there are significant overlaps among the sets of PTC-introducing AS events affected by individual knockdown of the three core human NMD factors, Up-Frameshift 1 (UPF1), UPF2, and UPF3X/B. However, the levels of some PTC-containing splice variants are less or not detectably affected by the knockdown of UPF2 and/or UPF3X, compared with the knockdown of UPF1. The intron sequences flanking the affected alternative exons are often highly conserved, suggesting important regulatory roles for these AS events. The corresponding genes represent diverse cellular functions, and surprisingly, many encode core spliceosomal proteins and assembly factors. We further show that conserved, PTC-introducing AS events are enriched in genes that encode core spliceosomal proteins. Where tested, altering the expression levels of these core spliceosomal components affects the regulation of PTC-containing splice variants from the corresponding genes. Together, our results show that AS-coupled NMD can have different UPF factor requirements and is likely to regulate many general components of the spliceosome. The results further implicate general spliceosomal components in AS regulation.

scholarly journals Identification of a translocated gating charge in a voltage-dependent channel. Colicin E1 channels in planar phospholipid bilayer membranes.

1991 ◽  
Vol 98 (1) ◽  
pp. 77-93 ◽  
Author(s):  
C K Abrams ◽  
K S Jakes ◽  
A Finkelstein ◽  
S L Slatin
Keyword(s):  
Voltage Dependence ◽  
Ion Selectivity ◽  
Lipid Vesicles ◽  
Voltage Gating ◽  
Site Directed Mutagenesis ◽  
Phospholipid Bilayer ◽  
Voltage Gated ◽  
Colicin E1 ◽  
Gating Charge ◽  
Ion Conducting

The availability of primary sequences for ion-conducting channels permits the development of testable models for mechanisms of voltage gating. Previous work on planar phospholipid bilayers and lipid vesicles indicates that voltage gating of colicin E1 channels involves translocation of peptide segments of the molecule into and across the membrane. Here we identify histidine residue 440 as a gating charge associated with this translocation. Using site-directed mutagenesis to convert the positively charged His440 to a neutral cysteine, we find that the voltage dependence for turn-off of channels formed by this mutant at position 440 is less steep than that for wild-type channels; the magnitude of the change in voltage dependence is consistent with residue 440 moving from the trans to the cis side of the membrane in association with channel closure. The effect of trans pH changes on the ion selectivity of channels formed by the carboxymethylated derivative of the cysteine 440 mutant independently establishes that in the open channel state, residue 440 lies on the trans side of the membrane. On the basis of these results, we propose that the voltage-gated opening of colicin E1 channels is accompanied by the insertion into the bilayer of a helical hairpin loop extending from residue 420 to residue 459, and that voltage-gated closing is associated with the extrusion of this loop from the interior of the bilayer back to the cis side.

Characterization of voltage-dependent calcium currents in mouse motoneurons

1992 ◽  
Vol 68 (1) ◽  
pp. 85-92 ◽  
Author(s):  
M. Mynlieff ◽  
K. G. Beam
Keyword(s):  
Voltage Dependence ◽  
Low Voltage ◽  
Calcium Currents ◽  
Patch Clamp Technique ◽  
Maximal Amplitude ◽  
Time To Peak ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Channel Currents

1. Calcium channel currents were measured with the whole-cell patch clamp technique in cultured, identified mouse motoneurons. Three components of current were operationally defined on the basis of voltage dependence, kinetics, and pharmacology. 2. Test potentials to -50 mV or greater (10 mM external Ca2+) elicited a low-voltage activated T-type current that was transient (decaying to baseline in less than 200 ms) and had a relatively slow time to peak (20-50 ms). A 1-s prepulse to -45 mV produced approximately half-maximal inactivation of this T current. 3. Two high-voltage activated (HVA) components of current (1 transient and 1 sustained) were activated by test potentials to -20 mV or greater (10 mM external Ca2+). A 1-s prepulse to -35 mV produced approximately half-maximal inactivation of the transient component without affecting the sustained component. 4. When Ba2+ was substituted for Ca2+ as the charge carrier, activation of the HVA components was shifted in the hyperpolarizing direction, and the relative amplitude of the transient HVA component was reduced. 5. Amiloride (1-2 mM) caused a reversible, partial block of the T current without affecting the HVA components. 6. The dihydropyridine agonist isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-nitro-3- pyridine-carboxylate [(+)-SDZ 202-791, 100 nM-1 microM)] shifted the activation of the sustained component of HVA current to more negative potentials and increased its maximal amplitude. Additionally, (+)-SDZ 202-791 caused the appearance of a slowed component of tail current.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of three alternative splice variants associated with the Arabidopsis rhomboid protein gene At1g74130

Botany ◽  
2013 ◽  
Vol 91 (12) ◽  
pp. 840-849 ◽  
Author(s):  
Joshua Powles ◽  
Katharine Sedivy-Haley ◽  
Eric Chapman ◽  
Kenton Ko
Keyword(s):  
Alternative Splicing ◽  
Alternative Splice ◽  
Splice Variant ◽  
Serine Proteases ◽  
Transmembrane Domain ◽  
Splice Variants ◽  
Genes Encoding ◽  
Different Characteristics ◽  
Alternative Splice Variants

Rhomboid serine proteases are grouped into three main types — secretases, presenilin-like associated rhomboid-like (PARL) proteases, and “inactive” rhomboid proteins. Although the three rhomboid groups are distinct, the different types are likely to operate within the same cell or compartment, such as observed in the plastids of Arabidopsis. There are four distinct plastid rhomboid genes at play in Arabidopsis plastids, two for active types (At1g25290 and At5g25752) and two for inactive forms (At1g74130 and At1g74140). The number of working plastid rhomboids is further increased by alternative splicing, as reported for At1g25290. To understand how the plastid rhomboid system works, it is necessary to identify all rhomboid forms in play. To this end, this study was designed to examine the alternative splicing activities of At1g74130, one of the two genes encoding proteolytically “inactive” plastid rhomboids. The exon mapping and DNA sequencing results obtained here indicate the presence of three prominent alternative splice variants in the At1g74130 transcript population. The dominant splice variant, L, encodes the full-length protein. The other two splice variants, M and S, produce proteins lacking sections from the carboxyl transmembrane domain region. The splice variants M and S appear to be at levels with functional potential and appear to adjust relative to each other during development and in response to changes in the level of Tic40, a component of the plastid translocon. The splice variant proteins themselves exhibit different characteristics with respect to rhomboid protein–substrate interactions. These differences were observed in bacterial co-expression pull-down assays and in yeast mitochondrial studies. When considered together, the data suggest that the alternative splicing of At1g74130 bears functional significance in Arabidopsis and is likely to be part of a mechanism for diversifying plastid rhomboid function.

Shanghai Express

2019 ◽  
pp. 23-40
Author(s):  
James Phillips
Keyword(s):  
Supporting Evidence ◽  
Philosophical Question ◽  
Production Code ◽  
The Senses ◽  
The Difference ◽  
And Shifts

The chapter focuses on Shanghai Express (1932) and analyzes its handling of the themes of prostitution, faith, and appearance. Sternberg’s film turns on the demand of Shanghai Lily (Dietrich) to be trusted without supporting evidence and shifts the object of faith from that which lies behind appearances to appearance itself. A redefinition of spectacle follows from this: it is not a mere given of the senses but involves a comportment and agency on the spectator’s part. Playing with the appearance of prostitution, the film toys with the moral guidelines of the Production Code. The chapter argues that it thereby not only sees how far it can go, but it also makes a philosophical question out of appearance itself, examining how the trust in love differs from knowledge. The make-believe and Orientalism of its reconstructed China are of a piece with its problematization of the difference between appearance and reality.

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