Identification of a Phospholemman-like Protein from Shark Rectal Glands

Mahmmoud, Yasser A.; Vorum, Henrik; Cornelius, Flemming

doi:10.1074/jbc.m005168200

Cited by 109 publications

(79 citation statements)

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“…This suggests that the interaction between PLMS and the shark ␣-subunit could be controlled by protein kinase-mediated phosphorylation reactions in a similar way to that proposed for the phospholamban (PLN) regulation of the Ca-ATPase in cardiac tissue in response to hormonal stimulation (3)(4)(5)(6)(7). Furthermore, PKC phosphorylation of the C-terminal cytoplasmic domain of PLMS, or disruption of interactions within the transmembrane domain by treatment with nonsolubilizing concentrations of the non-ionic detergent C 12 E 8 have been shown to result in activation of the shark Na,KATPase by relieving the inhibitory effect of PLMS (21). This again emphasizes the implication of multiple domain interaction between FXYD regulatory proteins and Na,K-ATPase, as is the case for PLN regulation of Ca-ATPase.…”

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confidence: 85%

“…1 the sequence of PLMS contains several potential tryptic cleavage sites in the C-terminal cytoplasmic domain upstream of the phosphorylation motif. We have previously described how PKC phosphorylation of PLMS leads to Na,K-ATPase activation caused by impairing of the protein-protein interaction (21). To investigate the nature of such interaction between the PLMS C terminus and the Na,K-ATPase in further details we have undertaken studies to preferentially cleave the PLMS C terminus while keeping the ␣-subunit intact.…”

Section: Cloning and Sequencing Of Plms-the Initial Squalusmentioning

confidence: 99%

“…19 and 20). Originally, this idea was substantiated by the identification of a PLM homologue (phospholemman-like protein from shark, PLMS) that was shown to specifically interact with and modulate Na,K-ATPase in the shark rectal gland (21). Subsequent investigations by Crambert et al (22), who used a co-expression system to study the effects of mammalian FXYD1 on Na,KATPase activity, indicated that PLM interacts with and regulates Na,K-ATPase isoforms.…”

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confidence: 99%

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confidence: 99%

“…The C terminus of PLMS is heavily phosphorylated by PKC (21), as is the case for PLM (14). Co-immunoprecipitation experiments demonstrated that dephosphorylated PLMS associated more strongly with the ␣-subunit than PKC-phosphorylated PLMS (21). This suggests that the interaction between PLMS and the shark ␣-subunit could be controlled by protein kinase-mediated phosphorylation reactions in a similar way to that proposed for the phospholamban (PLN) regulation of the Ca-ATPase in cardiac tissue in response to hormonal stimulation (3)(4)(5)(6)(7).…”

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Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

Mahmmoud

Cramb

Maunsbach

et al. 2003

Journal of Biological Chemistry

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In Na,K-ATPase membrane preparations from shark rectal glands, we have previously identified an FXYD domain-containing protein, phospholemman-like protein from shark, PLMS. This protein was shown to associate and modulate shark Na,K-ATPase activity in vitro. Here we describe the complete coding sequence, expression, and cellular localization of PLMS in the rectal gland of the shark Squalus acanthias. The mature protein contained 74 amino acids, including the N-terminal FXYD motif and a C-terminal protein kinase multisite phosphorylation motif. The sequence is preceded by a 20 amino acid candidate cleavable signal sequence. Immunogold labeling of the Na,K-ATPase ␣-subunit and PLMS showed the presence of ␣ and PLMS in the basolateral membranes of the rectal gland cells and suggested their partial colocalization. Furthermore, through controlled proteolysis, the C terminus of PLMS containing the protein kinase phosphorylation domain can be specifically cleaved. Removal of this domain resulted in stimulation of maximal Na,K-ATPase activity, as well as several partial reactions. Both the E 1 ϳP 3 E 2 -P reaction, which is partially rate-limiting in shark, and the K ؉ deocclusion reaction, E 2 (K) 3 E 1 , are accelerated. The latter may explain the finding that the apparent Na ؉ affinity was increased by the specific C-terminal PLMS truncation. Thus, these data are consistent with a model where interaction of the phosphorylation domain of PLMS with the Na,K-ATPase ␣-subunit is important for the modulation of shark Na,K-ATPase activity.

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Section: Cloning and Sequencing Of Plms-the Initial Squalusmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

Mahmmoud

Cramb

Maunsbach

et al. 2003

Journal of Biological Chemistry

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Cryo‐electron microscopy of Na⁺,K⁺‐ATPase reveals how the extracellular gate locks in the E2·2K⁺ state

et al. 2022

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is one of the most important members of the P-type ion-translocating ATPases and plays a pivotal role in establishing electrochemical gradients for Na + and K + across the cell membrane. Presented here is a 3.3 Å resolution structure of NKA in the E2Á2K + state solved by cryoelectron microscopy. It is a stable state with two occluded K + after transferring three Na + into the extracellular medium and releasing inorganic phosphate bound to the cytoplasmic P domain. We describe how the extracellular ion pathway wide open in the E2P state becomes closed and locked in E2Á2K + , linked to events at the phosphorylation site more than 50 Å away. We also show, although at low resolution, how ATP binding to NKA in E2Á2K + relaxes the gating machinery and thereby accelerates the transition into the next step, that is, the release of K + into the cytoplasm, more than 100 times.

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Crystal structures of Na⁺,K⁺‐ATPase reveal the mechanism that converts the K⁺‐bound form to Na⁺‐bound form and opens and closes the cytoplasmic gate

et al. 2023

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Na+,K+‐ATPase (NKA) plays a pivotal role in establishing electrochemical gradients for Na+ and K+ across the cell membrane by alternating between the E1 (showing high affinity for Na+ and low affinity for K+) and E2 (low affinity to Na+ and high affinity to K+) forms. Presented here are two crystal structures of NKA in E1·Mg2+ and E1·3Na+ states at 2.9 and 2.8 Å resolution, respectively. These two E1 structures fill a gap in our description of the NKA reaction cycle based on the atomic structures. We describe how NKA converts the K+‐bound E2·2K+ form to an E1 (E1·Mg2+) form, which allows high‐affinity Na+ binding, eventually closing the cytoplasmic gate (in E1 ~ P·ADP·3Na+) after binding three Na+, while keeping the extracellular ion pathway sealed. We now understand previously unknown functional roles for several parts of NKA and that NKA uses even the lipid bilayer for gating the ion pathway.

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Identification of a Phospholemman-like Protein from Shark Rectal Glands

Cited by 109 publications

References 49 publications

Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

Cryo‐electron microscopy of Na⁺,K⁺‐ATPase reveals how the extracellular gate locks in the E2·2K⁺ state

Crystal structures of Na⁺,K⁺‐ATPase reveal the mechanism that converts the K⁺‐bound form to Na⁺‐bound form and opens and closes the cytoplasmic gate

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Identification of a Phospholemman-like Protein from Shark Rectal Glands

Cited by 109 publications

References 49 publications

Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

Cryo‐electron microscopy of Na+,K+‐ATPase reveals how the extracellular gate locks in the E2·2K+ state

Crystal structures of Na+,K+‐ATPase reveal the mechanism that converts the K+‐bound form to Na+‐bound form and opens and closes the cytoplasmic gate

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Cryo‐electron microscopy of Na⁺,K⁺‐ATPase reveals how the extracellular gate locks in the E2·2K⁺ state

Crystal structures of Na⁺,K⁺‐ATPase reveal the mechanism that converts the K⁺‐bound form to Na⁺‐bound form and opens and closes the cytoplasmic gate