scholarly journals PSD-95 and SAP97 Exhibit Distinct Mechanisms for Regulating K+ Channel Surface Expression and Clustering

2000 ◽  
Vol 148 (1) ◽  
pp. 147-157 ◽  
Author(s):  
Amanda M. Tiffany ◽  
Louis N. Manganas ◽  
Eunjoon Kim ◽  
Yi-Ping Hsueh ◽  
Morgan Sheng ◽  
...  

Mechanisms of ion channel clustering by cytoplasmic membrane-associated guanylate kinases such as postsynaptic density 95 (PSD-95) and synapse-associated protein 97 (SAP97) are poorly understood. Here, we investigated the interaction of PSD-95 and SAP97 with voltage-gated or Kv K+ channels. Using Kv channels with different surface expression properties, we found that clustering by PSD-95 depended on channel cell surface expression. Moreover, PSD-95–induced clusters of Kv1 K+ channels were present on the cell surface. This was most dramatically demonstrated for Kv1.2 K+ channels, where surface expression and clustering by PSD-95 were coincidentally promoted by coexpression with cytoplasmic Kvβ subunits. Consistent with a mechanism of plasma membrane channel–PSD-95 binding, coexpression with PSD-95 did not affect the intrinsic surface expression characteristics of the different Kv channels. In contrast, the interaction of Kv1 channels with SAP97 was independent of Kv1 surface expression, occurred intracellularly, and prevented further biosynthetic trafficking of Kv1 channels. As such, SAP97 binding caused an intracellular accumulation of each Kv1 channel tested, through the accretion of SAP97 channel clusters in large (3–5 μm) ER-derived intracellular membrane vesicles. Together, these data show that ion channel clustering by PSD-95 and SAP97 occurs by distinct mechanisms, and suggests that these channel-clustering proteins may play diverse roles in regulating the abundance and distribution of channels at synapses and other neuronal membrane specializations.

2007 ◽  
Vol 293 (1) ◽  
pp. C152-C161 ◽  
Author(s):  
Lian Zhang ◽  
Karyn Foster ◽  
Qiuju Li ◽  
Jeffrey R. Martens

The number of ion channels expressed on the cell surface shapes the complex electrical response of excitable cells. An imbalance in the ratio of inward and outward conducting channels is unfavorable and often detrimental. For example, over- or underexpression of voltage-gated K+ (Kv) channels can be cytotoxic and in some cases lead to disease. In this study, we demonstrated a novel role for S-acylation in Kv1.5 cell surface expression. In transfected fibroblasts, biochemical evidence showed that Kv1.5 is posttranslationally modified on both the NH2 and COOH termini via hydroxylamine-sensitive thioester bonds. Pharmacological inhibition of S-acylation, but not myristoylation, significantly decreased Kv1.5 expression and resulted in accumulation of channel protein in intracellular compartments and targeting for degradation. Channel protein degradation was rescued by treatment with proteasome inhibitors. Time course experiments revealed that S-acylation occurred in the biosynthetic pathway of nascent channel protein and showed that newly synthesized Kv1.5 protein, but not protein expressed on the cell surface, is sensitive to inhibitors of thioacylation. Sensitivity to inhibitors of S-acylation was governed by COOH-terminal, but not NH2-terminal, cysteines. Surprisingly, although intracellular cysteines were required for S-acylation, mutation of these residues resulted in an increase in Kv1.5 cell surface channel expression, suggesting that screening of free cysteines by fatty acylation is an important regulatory step in the quality control pathway. Together, these results show that S-acylation can regulate steady-state expression of Kv1.5.


2006 ◽  
Vol 281 (52) ◽  
pp. 40015-40023 ◽  
Author(s):  
Kshama D. Chandrasekhar ◽  
Tuba Bas ◽  
William R. Kobertz

2008 ◽  
Vol 295 (3) ◽  
pp. C732-C739 ◽  
Author(s):  
Jayasheel O. Eshcol ◽  
Anne Marie S. Harding ◽  
Tomonori Hattori ◽  
Vivian Costa ◽  
Michael J. Welsh ◽  
...  

Acid-sensing ion channel 3 (ASIC3) is a H+-gated cation channel primarily found in sensory neurons, where it may function as a pH sensor in response to metabolic disturbances or painful conditions. We previously found that ASIC3 interacts with the postsynaptic density protein PSD-95 through its COOH terminus, which leads to a decrease in ASIC3 cell surface expression and H+-gated current. PSD-95 has been implicated in recruiting proteins to lipid rafts, which are membrane microdomains rich in cholesterol and sphingolipids that organize receptor/signaling complexes. We found ASIC3 and PSD-95 coimmunoprecipitated within detergent-resistant membrane fractions. When cells were exposed to methyl-β-cyclodextrin to deplete membrane cholesterol and disrupt lipid rafts, PSD-95 localization to lipid raft fractions was abolished and no longer inhibited ASIC3 current. Likewise, mutation of two cysteine residues in PSD-95 that undergo palmitoylation (a lipid modification that targets PSD-95 to lipid rafts) prevented its inhibition of ASIC3 current and cell surface expression. In addition, we found that cell surface ASIC3 is enriched in the lipid raft fraction. These data suggest that PSD-95 and ASIC3 interact within lipid rafts and that this raft interaction is required for PSD-95 to modulate ASIC3.


2010 ◽  
Vol 286 (3) ◽  
pp. 1828-1835 ◽  
Author(s):  
Seung-Kuy Cha ◽  
Chunfa Huang ◽  
Yaxian Ding ◽  
Xiaoping Qi ◽  
Chou-Long Huang ◽  
...  

2010 ◽  
Vol 391 (2) ◽  
pp. 1262-1267 ◽  
Author(s):  
Brigitte Egenberger ◽  
Georg Polleichtner ◽  
Erhard Wischmeyer ◽  
Frank Döring

2020 ◽  
Author(s):  
Florent Colomb ◽  
Leila B. Giron ◽  
Leticia Kuri Cervantes ◽  
Tongcui Ma ◽  
Samson Adeniji ◽  
...  

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