Differential K+ channel clustering activity of PSD-95 and SAP97, two related membrane-associated putative guanylate kinases.
The molecular mechanisms underlying the clustering and localization of K+ channels in specific microdomains on the neuronal surface are largely unknown. The Shaker subclass of voltage-gated K+ channel alpha-subunits interact through their cytoplasmic C-terminus with a family of membrane-associated putative guanylate kinases, including PSD-95 and SAP97. We show here that heterologous coexpression of either sap97 or PSD-95 with various Shaker-type subunits results in the coclustering of these proteins with the K+ channels. Mutation of the C-terminal sequence (-ETDV) of the Shaker subunit Kv1.4 abolishes its binding to, and prevents its clustering with, SAP97 and PSD-95. Whereas PSD-95 induces plaque-like clusters of K+ channels at the cell surface; however, SAP97 coexpression results in the formation of large round intracellular aggregates into which both SAP97 and the K+ channel proteins are colocalized. The efficiency of surface clustering by PSD-95 varies with different Shaker subunits: striking Kv1.4 clustering occurs in > 60% of cotransfected cells, whereas Kv1.1 and Kv1.2 form convincing clusters with PSD-95 only in approximately 10% of cells.
Kim
E
E
Howard Hughes Medical Institute, Department of Neurobiology, Massachusetts General Hospital, Boston 02114, USA.
Sheng
M
M
D000818:Animals; D019556:COS Cells; D051528:Guanylate Kinases; D051662:Kv1.1 Potassium Channel; D051665:Kv1.4 Potassium Channel; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D011485:Protein Binding; D051637:Shaker Superfamily of Potassium Channels; D014162:Transfection
D051665:Kv1.4 Potassium Channel; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051637:Shaker Superfamily of Potassium Channels; C033652:postsynaptic density proteins; D051662:Kv1.1 Potassium Channel; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases