Effects of Phospholipids on the Oligomeric State of Phospholamban of the Cardiac Sarcoplasmic Reticulum

Zhang, Xiao Ming; Kimura, Yuichi; Inui, Makoto

doi:10.1253/circj.69.1116

Cited by 14 publications

(10 citation statements)

References 35 publications

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“…It has been hypothesized that its interactions with lipid membranes are important for both oligomerization (49) and SERCA regulation (50). The T-state structure of PLN reported here reveals that both interprotomer interactions and lipid/protein interactions contribute to the overall folding and stability.…”

Section: Discussionmentioning

confidence: 68%

Structural topology of phospholamban pentamer in lipid bilayers by a hybrid solution and solid-state NMR method

Verardi

Shi

Traaseth

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

155

210

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Phospholamban (PLN) is a type II membrane protein that inhibits the sarcoplasmic reticulum Ca 2þ -ATPase (SERCA), thereby regulating calcium homeostasis in cardiac muscle. In membranes, PLN forms pentamers that have been proposed to function either as a storage for active monomers or as ion channels. Here, we report the T-state structure of pentameric PLN solved by a hybrid solution and solid-state NMR method. In lipid bilayers, PLN adopts a pinwheel topology with a narrow hydrophobic pore, which excludes ion transport. In the T state, the cytoplasmic amphipathic helices (domains Ia) are absorbed into the lipid bilayer with the transmembrane domains arranged in a left-handed coiled-coil configuration, crossing the bilayer with a tilt angle of approximately 11°with respect to the membrane normal. The tilt angle difference between the monomer and pentamer is approximately 13°, showing that intramembrane helix-helix association forces dominate over the hydrophobic mismatch, driving the overall topology of the transmembrane assembly. Our data reveal that both topology and function of PLN are shaped by the interactions with lipids, which fine-tune the regulation of SERCA.hybrid NMR method | PISEMA | calcium regulation | oligomeric protein | dipolar assisted rotational resonance recoupling T he membrane protein complex formed by Ca 2þ -ATPase (SERCA) and phospholamban (PLN) regulates Ca 2þ concentration within the sarcoplasmic reticulum (SR), thereby controlling muscle excitation-contraction coupling (1, 2). PLN is a 52-residue transmembrane (TM) protein highly conserved across mammals (2). Its helix-loop-helix secondary structure is further subdivided into four dynamic domains: domain Ia (1-16), loop (17)(18)(19)(20)(21)(22), and domain II (31-52) (3, 4). The hydrophobic TM domain II is the most conserved and responsible for SERCA inhibition, whereas the cytoplasmic domain harbors two phosphorylation sites that reverse PLN inhibitory function (2). PLN has a direct role in the pathophysiology of the heart muscle, with three lethal mutations linked to dilated cardiomyopathy in humans (R9C-PLN, R14del, and L39-truncated-PLN) (5). In both synthetic and cell membranes, PLN forms pentamers that dissociate into monomers upon interacting with SERCA (1, 6). Although the stoichiometry of the SERCA/PLN complex has been assessed (1, 6), both the role and the structure of the PLN pentamer remain a matter of active debate. Because PLN expression in both atria and ventricles is higher than SERCA, it is likely that oligomerization may participate in SERCA regulation (7). Insights into PLN organization in the membrane have come from biochemical and biophysical data (2,6,8). Initial electrophysiological measurements indicated that PLN formed Ca 2þ channels (9). However, more recent electrochemical studies concluded that PLN does not conduct Cl − or Ca 2þ ions (10).Divergent structural models for the PLN pentamer have been proposed in the literature (8). Although very similar in the secondary structure content, these models differ in t...

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Section: Discussionmentioning

confidence: 68%

Structural topology of phospholamban pentamer in lipid bilayers by a hybrid solution and solid-state NMR method

Verardi

Shi

Traaseth

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

155

210

View full text Add to dashboard Cite

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“…8). Along these lines, lyso-PC and lyso-PE have been shown to stabilize the pentameric form of the membrane protein, phospholamban, and prevent its dissociation to monomers (58). It is hypothesized that membrane insertion of these perturbing, cone-shaped lipids (18, 33-35, 51, 59) supports G2A dimerization/oligomerization (56,57).…”

Section: Discussionmentioning

confidence: 99%

Lysophospholipids of Different Classes Mobilize Neutrophil Secretory Vesicles and Induce Redundant Signaling through G2A

Frasch

Berry²,

Murphy³

et al. 2007

The Journal of Immunology

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Lysophosphatidylcholine has been shown to enhance neutrophil functions through a mechanism involving the G protein-coupled receptor G2A. Recent data support an indirect effect of lysophosphatidylcholine on G2A rather than direct ligand binding. These observations prompted the hypothesis that other lysophospholipids (lyso-PLs) may also signal for human neutrophil activation through G2A. To this end, 1-oleoyl-2-hydroxy-sn-glycero-3-[phospho-l-choline], but also C18:1/OH lyso-PLs bearing the phosphoserine and phosphoethanolamine head groups, presented on albumin, were shown to signal for calcium flux in a self- and cross-desensitizing manner, implicating a single receptor. Blocking Abs to G2A inhibited calcium signaling by all three lyso-PLs. Furthermore, inhibition by both pertussis toxin and U-73122 established signaling via the Gαi/phospholipase C pathway for calcium mobilization. Altered plasma membrane localization of G2A has been hypothesized to facilitate signaling. Accordingly, an increase in detectable G2A was demonstrated by 1 min after lyso-PL stimulation and was followed by visible patching of the receptor. Western blotting showed that G2A resides in the plasma membrane/secretory vesicle fraction and not in neutrophil primary, secondary, or tertiary granules. Enhanced detection of G2A induced by lyso-PLs was paralleled by enhanced detection of CD45, confirming mobilization of the labile secretory vesicle pool. Together, these data show that lyso-PLs bearing various head groups redundantly mobilize G2A latent within secretory vesicles and result in G2A receptor/Gαi/phospholipase C signaling for calcium flux in neutrophils.

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“…Protein preparation and Western blot analysis were performed using the techniques described previously (Greering et al, 1989;Zhang et al, 2005) with minor modifications. Briefly, native human RPE sheets were placed into buffer A (150 mM NaCl, 20 mM Tris-HCl [pH 7.4], 2 mM EDTA, 2% sodium dodecyl sulfate (SDS) containing complete protease inhibitor cocktail (Pierce Rockford, IL), and 10 mM 2-mercaptoethanol) and homogenized.…”

Section: Western Blot Analysismentioning

confidence: 99%

Expression of Kir7.1 and a novel Kir7.1 splice variant in native human retinal pigment epithelium

Yang

Swaminathan

Zhang

et al. 2008

Experimental Eye Research

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Previous studies on bovine retinal pigment epithelium (RPE) established that Kir7.1 channels compose this epithelium's large apical membrane K+ conductance. The purpose of this study was to determine whether Kir7.1 and potential Kir7.1 splice variants are expressed in native adult human RPE and, if so, to determine their function and how they are generated. RT-PCR analysis indicated that human RPE expresses full-length Kir7.1 and a novel Kir7.1 splice variant, designated Kir7.1S. Analysis of the human Kir7.1 gene (KCNJ13) organization revealed that it contains three exons, two introns, and a novel alternative 5' splice site in exon 2. In human RPE, the alternative usage of two competing 5' splice sites in exon 2 gives rise to transcripts encoding full-length Kir7.1 and Kir7.1S, which is predicted to encode a truncated protein. Real-time PCR indicated that Kir7.1 transcript is nearly as abundant as GAPDH mRNA in human RPE whereas Kir7.1S transcript expression is 4-fold lower. Western blot analysis showed that the splice variant is translated in Xenopus oocytes injected with Kir7.1S cRNA and revealed the expression of full-length Kir7.1 but not Kir7.1S in adult human RPE. Co-expression of Kir7.1 with Kir7.1S in Xenopus oocytes had no effect on either the kinetics or amplitude of Kir7.1 currents. This study confirms the expression of Kir7.1 in human RPE, identifies a Kir7.1 splice variant resulting in predicted changes in protein sequence, and indicates that there is no functional interaction between this splice variant and full-length Kir7.1.

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Effects of Phospholipids on the Oligomeric State of Phospholamban of the Cardiac Sarcoplasmic Reticulum

Cited by 14 publications

References 35 publications

Structural topology of phospholamban pentamer in lipid bilayers by a hybrid solution and solid-state NMR method

Structural topology of phospholamban pentamer in lipid bilayers by a hybrid solution and solid-state NMR method

Lysophospholipids of Different Classes Mobilize Neutrophil Secretory Vesicles and Induce Redundant Signaling through G2A

Expression of Kir7.1 and a novel Kir7.1 splice variant in native human retinal pigment epithelium

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