The Journal of General Physiology最新文献

{"title":"KCNQ1 subdomains involved in KCNE modulation revealed by an invertebrate KCNQ1 orthologue.","authors":"Koichi Nakajo,&nbsp;Atsuo Nishino,&nbsp;Yasushi Okamura,&nbsp;Yoshihiro Kubo","doi":"10.1085/jgp.201110677","DOIUrl":"https://doi.org/10.1085/jgp.201110677","url":null,"abstract":"<p><p>KCNQ1 channels are voltage-gated potassium channels that are widely expressed in various non-neuronal tissues, such as the heart, pancreas, and intestine. KCNE proteins are known as the auxiliary subunits for KCNQ1 channels. The effects and functions of the different KCNE proteins on KCNQ1 modulation are various; the KCNQ1-KCNE1 ion channel complex produces a slowly activating potassium channel that is crucial for heartbeat regulation, while the KCNE3 protein makes KCNQ1 channels constitutively active, which is important for K(+) and Cl(-) transport in the intestine. The mechanisms by which KCNE proteins modulate KCNQ1 channels have long been studied and discussed; however, it is not well understood how different KCNE proteins exert considerably different effects on KCNQ1 channels. Here, we approached this point by taking advantage of the recently isolated Ci-KCNQ1, a KCNQ1 homologue from marine invertebrate Ciona intestinalis. We found that Ci-KCNQ1 alone could be expressed in Xenopus laevis oocytes and produced a voltage-dependent potassium current, but that Ci-KCNQ1 was not properly modulated by KCNE1 and totally unaffected by coexpression of KCNE3. By making chimeras of Ci-KCNQ1 and human KCNQ1, we determined several amino acid residues located in the pore region of human KCNQ1 involved in KCNE1 modulation. Interestingly, though, these amino acid residues of the pore region are not important for KCNE3 modulation, and we subsequently found that the S1 segment plays an important role in making KCNQ1 channels constitutively active by KCNE3. Our findings indicate that different KCNE proteins use different domains of KCNQ1 channels, and that may explain why different KCNE proteins give quite different outcomes by forming a complex with KCNQ1 channels.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"521-35"},"PeriodicalIF":3.8,"publicationDate":"2011-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201110677","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40120390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Involvement of F1296 and N1303 of CFTR in induced-fit conformational change in response to ATP binding at NBD2.","authors":"Andras Szollosi, Paola Vergani, László Csanády","doi":"10.1085/jgp.201010434","DOIUrl":"10.1085/jgp.201010434","url":null,"abstract":"<p><p>The chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) displays a typical adenosine trisphosphate (ATP)-binding cassette (ABC) protein architecture comprising two transmembrane domains, two intracellular nucleotide-binding domains (NBDs), and a unique intracellular regulatory domain. Once phosphorylated in the regulatory domain, CFTR channels can open and close when supplied with cytosolic ATP. Despite the general agreement that formation of a head-to-tail NBD dimer drives the opening of the chloride ion pore, little is known about how ATP binding to individual NBDs promotes subsequent formation of this stable dimer. Structural studies on isolated NBDs suggest that ATP binding induces an intra-domain conformational change termed \"induced fit,\" which is required for subsequent dimerization. We investigated the allosteric interaction between three residues within NBD2 of CFTR, F1296, N1303, and R1358, because statistical coupling analysis suggests coevolution of these positions, and because in crystal structures of ABC domains, interactions between these positions appear to be modulated by ATP binding. We expressed wild-type as well as F1296S, N1303Q, and R1358A mutant CFTR in Xenopus oocytes and studied these channels using macroscopic inside-out patch recordings. Thermodynamic mutant cycles were built on several kinetic parameters that characterize individual steps in the gating cycle, such as apparent affinities for ATP, open probabilities in the absence of ATP, open probabilities in saturating ATP in a mutant background (K1250R), which precludes ATP hydrolysis, as well as the rates of nonhydrolytic closure. Our results suggest state-dependent changes in coupling between two of the three positions (1296 and 1303) and are consistent with a model that assumes a toggle switch-like interaction pattern during the intra-NBD2 induced fit in response to ATP binding. Stabilizing interactions of F1296 and N1303 present before ATP binding are replaced by a single F1296-N1303 contact in ATP-bound states, with similar interaction partner toggling occurring during the much rarer ATP-independent spontaneous openings.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"407-23"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/98/cf/JGP_201010434.PMC2947058.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29308326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An improved open-channel structure of MscL determined from FRET confocal microscopy and simulation.","authors":"Ben Corry,&nbsp;Annette C Hurst,&nbsp;Prithwish Pal,&nbsp;Takeshi Nomura,&nbsp;Paul Rigby,&nbsp;Boris Martinac","doi":"10.1085/jgp.200910376","DOIUrl":"https://doi.org/10.1085/jgp.200910376","url":null,"abstract":"<p><p>Mechanosensitive channels act as molecular transducers of mechanical force exerted on the membrane of living cells by opening in response to membrane bilayer deformations occurring in physiological processes such as touch, hearing, blood pressure regulation, and osmoregulation. Here, we determine the likely structure of the open state of the mechanosensitive channel of large conductance using a combination of patch clamp, fluorescence resonance energy transfer (FRET) spectroscopy, data from previous electron paramagnetic resonance experiments, and molecular and Brownian dynamics simulations. We show that structural rearrangements of the protein can be measured in similar conditions as patch clamp recordings while controlling the state of the pore in its natural lipid environment by modifying the lateral pressure distribution via the lipid bilayer. Transition to the open state is less dramatic than previously proposed, while the N terminus remains anchored at the surface of the membrane where it can either guide the tilt of or directly translate membrane tension to the conformation of the pore-lining helix. Combining FRET data obtained in physiological conditions with simulations is likely to be of great value for studying conformational changes in a range of multimeric membrane proteins.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"483-94"},"PeriodicalIF":3.8,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.200910376","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29310942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neuroglial ATP release through innexin channels controls microglial cell movement to a nerve injury.","authors":"Stuart E Samuels,&nbsp;Jeffrey B Lipitz,&nbsp;Gerhard Dahl,&nbsp;Kenneth J Muller","doi":"10.1085/jgp.201010476","DOIUrl":"https://doi.org/10.1085/jgp.201010476","url":null,"abstract":"<p><p>Microglia, the immune cells of the central nervous system, are attracted to sites of injury. The injury releases adenosine triphosphate (ATP) into the extracellular space, activating the microglia, but the full mechanism of release is not known. In glial cells, a family of physiologically regulated unpaired gap junction channels called innexons (invertebrates) or pannexons (vertebrates) located in the cell membrane is permeable to ATP. Innexons, but not pannexons, also pair to make gap junctions. Glial calcium waves, triggered by injury or mechanical stimulation, open pannexon/innexon channels and cause the release of ATP. It has been hypothesized that a glial calcium wave that triggers the release of ATP causes rapid microglial migration to distant lesions. In the present study in the leech, in which a single giant glial cell ensheathes each connective, hydrolysis of ATP with 10 U/ml apyrase or block of innexons with 10 µM carbenoxolone (CBX), which decreased injury-induced ATP release, reduced both movement of microglia and their accumulation at lesions. Directed movement and accumulation were restored in CBX by adding ATP, consistent with separate actions of ATP and nitric oxide, which is required for directed movement but does not activate glia. Injection of glia with innexin2 (Hminx2) RNAi inhibited release of carboxyfluorescein dye and microglial migration, whereas injection of innexin1 (Hminx1) RNAi did not when measured 2 days after injection, indicating that glial cells' ATP release through innexons was required for microglial migration after nerve injury. Focal stimulation either mechanically or with ATP generated a calcium wave in the glial cell; injury caused a large, persistent intracellular calcium response. Neither the calcium wave nor the persistent response required ATP or its release. Thus, in the leech, innexin membrane channels releasing ATP from glia are required for migration and accumulation of microglia after nerve injury.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"425-42"},"PeriodicalIF":3.8,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201010476","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29310940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of the PCMBS-dependent modification of KCa3.1 channel gating.","authors":"Mark A Bailey,&nbsp;Michael Grabe,&nbsp;Daniel C Devor","doi":"10.1085/jgp.201010430","DOIUrl":"https://doi.org/10.1085/jgp.201010430","url":null,"abstract":"<p><p>Intermediate conductance, calcium-activated potassium channels are gated by the binding of intracellular Ca(2+) to calmodulin, a Ca(2+)-binding protein that is constitutively associated with the C terminus of the channel. Although previous studies indicated that the pore-lining residues along the C-terminal portion of S6 contribute to the activation mechanism, little is known about whether the nonluminal face of S6 contributes to this process. Here we demonstrate that the sulfhydral reagent, parachloromercuribenze sulfonate (PCMBS), modifies an endogenous cysteine residue predicted to have a nonluminal orientation (Cys(276)) along the sixth transmembrane segment (S6). Modification of Cys(276) manipulates the steady-state and kinetic behavior of the channel by shifting the gating equilibrium toward the open state, resulting in a left shift in apparent Ca(2+) affinity and a slowing in the deactivation process. Using a six-state gating scheme, our analysis shows that PCMBS slows the transition between the open state back to the third closed state. Interpreting this result in the context of the steady-state and kinetic data suggests that PCMBS functions to shift the gating equilibrium toward the open state by disrupting channel closing. In an attempt to understand whether the nonluminal face of S6 participates in the activation mechanism, we conducted a partial tryptophan scan of this region. Substituting a tryptophan for Leu(281) recapitulated the effect on the steady-state and kinetic behavior observed with PCMBS. Considering the predicted nonluminal orientation of Cys(276) and Leu(281), a simple physical interpretation of these results is that the nonluminal face of S6 forms a critical interaction surface mediating the transition into the closed conformation, suggesting the nonluminal C-terminal portion of S6 is allosterically coupled to the activation gate.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"367-87"},"PeriodicalIF":3.8,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201010430","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40066039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coordinated control of sensitivity by two splice variants of Gα(o) in retinal ON bipolar cells.","authors":"Haruhisa Okawa, Johan Pahlberg, Fred Rieke, Lutz Birnbaumer, Alapakkam P Sampath","doi":"10.1085/jgp.201010477","DOIUrl":"10.1085/jgp.201010477","url":null,"abstract":"<p><p>The high sensitivity of scotopic vision depends on the efficient retinal processing of single photon responses generated by individual rod photoreceptors. At the first synapse in the mammalian retina, rod outputs are pooled by a rod \"ON\" bipolar cell, which uses a G-protein signaling cascade to enhance the fidelity of the single photon response under conditions where few rods absorb light. Here we show in mouse rod bipolar cells that both splice variants of the G(o) α subunit, Gα(o1) and Gα(o2), mediate light responses under the control of mGluR6 receptors, and their coordinated action is critical for maximizing sensitivity. We found that the light response of rod bipolar cells was primarily mediated by Gα(o1), but the loss of Gα(o2) caused a reduction in the light sensitivity. This reduced sensitivity was not attributable to the reduction in the total number of G(o) α subunits, or the altered balance of expression levels between the two splice variants. These results indicate that Gα(o1) and Gα(o2) both mediate a depolarizing light response in rod bipolar cells without occluding each other's actions, suggesting they might act independently on a common effector. Thus, Gα(o2) plays a role in improving the sensitivity of rod bipolar cells through its action with Gα(o1). The coordinated action of two splice variants of a single Gα may represent a novel mechanism for the fine control of G-protein activity.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"443-54"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/d6/cd/JGP_201010477.PMC2947061.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40064860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regulatory mechanism of length-dependent activation in skinned porcine ventricular muscle: role of thin filament cooperative activation in the Frank-Starling relation.","authors":"Takako Terui,&nbsp;Yuta Shimamoto,&nbsp;Mitsunori Yamane,&nbsp;Fuyu Kobirumaki,&nbsp;Iwao Ohtsuki,&nbsp;Shin'ichi Ishiwata,&nbsp;Satoshi Kurihara,&nbsp;Norio Fukuda","doi":"10.1085/jgp.201010502","DOIUrl":"https://doi.org/10.1085/jgp.201010502","url":null,"abstract":"<p><p>Cardiac sarcomeres produce greater active force in response to stretch, forming the basis of the Frank-Starling mechanism of the heart. The purpose of this study was to provide the systematic understanding of length-dependent activation by investigating experimentally and mathematically how the thin filament \"on-off\" switching mechanism is involved in its regulation. Porcine left ventricular muscles were skinned, and force measurements were performed at short (1.9 µm) and long (2.3 µm) sarcomere lengths. We found that 3 mM MgADP increased Ca(2+) sensitivity of force and the rate of rise of active force, consistent with the increase in thin filament cooperative activation. MgADP attenuated length-dependent activation with and without thin filament reconstitution with the fast skeletal troponin complex (sTn). Conversely, 20 mM of inorganic phosphate (Pi) decreased Ca(2+) sensitivity of force and the rate of rise of active force, consistent with the decrease in thin filament cooperative activation. Pi enhanced length-dependent activation with and without sTn reconstitution. Linear regression analysis revealed that the magnitude of length-dependent activation was inversely correlated with the rate of rise of active force. These results were quantitatively simulated by a model that incorporates the Ca(2+)-dependent on-off switching of the thin filament state and interfilament lattice spacing modulation. Our model analysis revealed that the cooperativity of the thin filament on-off switching, but not the Ca(2+)-binding ability, determines the magnitude of the Frank-Starling effect. These findings demonstrate that the Frank-Starling relation is strongly influenced by thin filament cooperative activation.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"469-82"},"PeriodicalIF":3.8,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201010502","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29310941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"IP(3)-dependent, post-tetanic calcium transients induced by electrostimulation of adult skeletal muscle fibers.","authors":"Mariana Casas,&nbsp;Reinaldo Figueroa,&nbsp;Gonzalo Jorquera,&nbsp;Matías Escobar,&nbsp;Jordi Molgó,&nbsp;Enrique Jaimovich","doi":"10.1085/jgp.200910397","DOIUrl":"https://doi.org/10.1085/jgp.200910397","url":null,"abstract":"<p><p>Tetanic electrical stimulation induces two separate calcium signals in rat skeletal myotubes, a fast one, dependent on Cav 1.1 or dihydropyridine receptors (DHPRs) and ryanodine receptors and related to contraction, and a slow signal, dependent on DHPR and inositol trisphosphate receptors (IP(3)Rs) and related to transcriptional events. We searched for slow calcium signals in adult muscle fibers using isolated adult flexor digitorum brevis fibers from 5-7-wk-old mice, loaded with fluo-3. When stimulated with trains of 0.3-ms pulses at various frequencies, cells responded with a fast calcium signal associated with muscle contraction, followed by a slower signal similar to one previously described in cultured myotubes. Nifedipine inhibited the slow signal more effectively than the fast one, suggesting a role for DHPR in its onset. The IP(3)R inhibitors Xestospongin B or C (5 µM) also inhibited it. The amplitude of post-tetanic calcium transients depends on both tetanus frequency and duration, having a maximum at 10-20 Hz. At this stimulation frequency, an increase of the slow isoform of troponin I mRNA was detected, while the fast isoform of this gene was inhibited. All three IP(3)R isoforms were present in adult muscle. IP(3)R-1 was differentially expressed in different types of muscle fibers, being higher in a subset of fast-type fibers. Interestingly, isolated fibers from the slow soleus muscle did not reveal the slow calcium signal induced by electrical stimulus. These results support the idea that IP(3)R-dependent slow calcium signals may be characteristic of distinct types of muscle fibers and may participate in the activation of specific transcriptional programs of slow and fast phenotype.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"455-67"},"PeriodicalIF":3.8,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.200910397","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40064861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring atomic resolution physiology on a femtosecond to millisecond timescale using molecular dynamics simulations.","authors":"Ron O Dror,&nbsp;Morten Ø Jensen,&nbsp;David W Borhani,&nbsp;David E Shaw","doi":"10.1085/jgp.200910373","DOIUrl":"https://doi.org/10.1085/jgp.200910373","url":null,"abstract":"","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"555-62"},"PeriodicalIF":3.8,"publicationDate":"2010-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.200910373","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29026109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adaptive behavior of bacterial mechanosensitive channels is coupled to membrane mechanics.","authors":"Vladislav Belyy,&nbsp;Kishore Kamaraju,&nbsp;Bradley Akitake,&nbsp;Andriy Anishkin,&nbsp;Sergei Sukharev","doi":"10.1085/jgp.200910371","DOIUrl":"https://doi.org/10.1085/jgp.200910371","url":null,"abstract":"<p><p>Mechanosensitive channel of small conductance (MscS), a tension-driven osmolyte release valve residing in the inner membrane of Escherichia coli, exhibits a complex adaptive behavior, whereas its functional counterpart, mechanosensitive channel of large conductance (MscL), was generally considered nonadaptive. In this study, we show that both channels exhibit similar adaptation in excised patches, a process that is completely separable from inactivation prominent only in MscS. When a membrane patch is held under constant pressure, adaptation of both channels is manifested as a reversible current decline. Their dose-response curves recorded with 1-10-s ramps of pressure are shifted toward higher tension relative to the curves measured with series of pulses, indicating decreased tension sensitivity. Prolonged exposure of excised patches to subthreshold tensions further shifts activation curves for both MscS and MscL toward higher tension with similar magnitude and time course. Whole spheroplast MscS recordings performed with simultaneous imaging reveal activation curves with a midpoint tension of 7.8 mN/m and the slope corresponding to approximately 15-nm(2) in-plane expansion. Inactivation was retained in whole spheroplast mode, but no adaptation was observed. Similarly, whole spheroplast recordings of MscL (V23T mutant) indicated no adaptation, which was present in excised patches. MscS activities tried in spheroplast-attached mode showed no adaptation when the spheroplasts were intact, but permeabilized spheroplasts showed delayed adaptation, suggesting that the presence of membrane breaks or edges causes adaptation. We interpret this in the framework of the mechanics of the bilayer couple linking adaptation of channels in excised patches to the relaxation of the inner leaflet that is not in contact with the glass pipette. Relaxation of one leaflet results in asymmetric redistribution of tension in the bilayer that is less favorable for channel opening.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"641-52"},"PeriodicalIF":3.8,"publicationDate":"2010-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.200910371","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29026112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}