Differential Recruitment of Kv1.4 and Kv4.2 to Lipid Rafts by PSD-95
Notice bibliographique
Résumé
The activity of voltage-gated potassium (Kv) channels, and consequently their influence on cellular functions, can be substantially altered by phosphorylation.Several protein kinases that modulate Kv channel activity are found in membrane subdomains known as lipid rafts, which are thought to organize signaling complexes in the cell.Thus, we asked whether Kv1.4 and Kv4.2, two channels with critical roles in excitable cells, are found in lipid rafts.Acylation can target proteins to raft regions; however, Kv channels are not acylated, and therefore, a different mechanism must exist to bring them into these membrane subdomains.Because both Kv1.4 and Kv4.2 interact with postsynaptic density protein 95 (PSD-95), which is acylated (specifically, palmitoylated), we examined whether PSD-95 can recruit these channels to lipid rafts.We found that a portion of Kv1.4 and Kv4.2 protein in rat brain membranes is raftassociated.Lipid raft patching and immunostaining confirmed that some Kv4.2 is in Thy-1-containing rafts in rat hippocampal neurons.Using a heterologous expression system, we determined that palmitoylation of PSD-95 was crucial to its localization to lipid rafts.We then assessed the contribution of PSD-95 to the raft association of these channels.Co-expression of PSD-95 increased the amount of Kv1.4, but not Kv4.2, in lipid rafts.Deleting the PSD-95 binding motif of Kv1.4 eliminated this recruitment, as did substituting a palmitoylation-deficient PSD-95 mutant.This work represents the first evidence that PSD-95 binding can recruit Kv channels into lipid rafts, a process that could facilitate interactions with the protein kinases that affect channel activity.Voltage-gated potassium (Kv) 1 channels are important determinants of the resting membrane potential and other electrophysiological properties of excitable cells such as neurons and myocytes.In particular, it has been suggested that Kv1.4, which is located axonally and presynaptically (1), modulates action potential propagation (2) and neurotransmitter release (3).In contrast, Kv4.2 is localized to the somatodendritic region of neurons (4), where it is poised to influence the excitability of the postsynaptic membrane (5, 6).The activity of these channels, and therefore their influence on cellular functions, can be significantly altered by protein kinases and phosphatases.The activity of Kv1.4 is known to be affected by protein kinase C (PKC) (7) and tyrosine kinases (8), while Kv4.2 can be phosphorylated by protein kinase A (PKA) (9), PKC (10), and the extracellular signal-related kinase (ERK) (6).Certain isoforms of the above kinases are found in membrane microdomains known as lipid rafts, which are enriched in cholesterol and sphingolipids and are thought to exist in a "liquid-order" state that is distinct from the more fluid, disordered state exhibited by surrounding phospholipids (11,12).This tightly ordered array of cholesterol and sphingolipids more readily incorporates molecules with saturated, unbranched side chains and tends to exclude molecules with unsaturated side chains.Thus, many proteins that reside in rafts, including several protein kinases, G proteins and other members of signal transduction cascades, are often acylated, particularly myristoylated and/or palmitoylated (13).In some cases, this acylation can serve as a targeting signal for lipid rafts (13).The enrichment of signaling molecules in lipid rafts has led to speculation that these microdomains serve to organize and concentrate signaling complexes in the cell.Kv1.4 and Kv4.2 are not known to be acylated.Thus, if they are present in lipid rafts, the mechanism by which they are recruited is not known.Therefore, we first determined if these Kv channels are found in lipid rafts.Both Kv channels interact with postsynaptic density protein 95 (PSD-95) (14, 15), a PSD-95/Dlg/ZO-1 (PDZ) domain protein, which is acylated (specifically, palmitoylated, Ref. 16).Accordingly, we also assessed whether PSD-95 can recruit these channels to lipid rafts.We show that a portion of Kv1.4,Kv4.2, and PSD-95 protein in rat brain membranes is found in lipid raft fractions.We then exploited heterologous expression to determine the role of palmitoylation in the targeting of PSD-95 to raft regions, and demonstrate that a palmitoylation-deficient PSD-95 mutant is not trafficked to rafts.Next, we assessed the contribution of PSD-95 to the lipid raft localization of Kv1.4 and Kv4.2.Coexpression of PSD-95 increased the amount of Kv1.4, but not Kv4.2, in lipid rafts, and substituting a palmitoylation-defi-
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».