title: Requirement of N-terminal cysteines of PSD-95 for PSD-95 multimerization and ternary complex formation, but not for binding to potassium channel Kv1.4.
abstract: The PSD-95 family of PSD-95/Discs large/ZO-1 (PDZ) domain-containing proteins plays a role in the clustering and localization of specific ion channels and receptors at synapses. Previous studies have shown that PSD-95 forms multimers through an N-terminal region (termed the N-segment) and that the multimerization of PSD-95 is critical for its ability to cluster Shaker-type potassium channel Kv1.4 in heterologous cells. We show here that the PSD-95 N-segment functions as a multimerization domain only when located at the N-terminal end of a heterologous protein. A pair of N-terminal cysteines, Cys3 and Cys5, is essential for the ability of PSD-95 to self-associate and to form cell surface clusters with Kv1.4. However, PSD-95 mutants lacking these cysteine residues retain their ability to associate with membranes and to bind to Kv1.4. Unlike wild type PSD-95, the cysteine mutant of PSD-95 cannot form a ternary complex with Kv1.4 and the cell adhesion molecule Fasciclin II. These results suggest that the N-terminal cysteines are essential for PSD-95 multimerization and that multimerization is required for simultaneous binding of multiple membrane protein ligands by PSD-95.
authors.affiliation: Howard Hughes Medical Institute and Department of Neurobiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Y P
authors.initials: YP
authors.lastname: Hsueh
authors.forename: M
authors.initials: M
authors.lastname: Sheng
mesh_terms: D000818:Animals; D001704:Biopolymers; D019556:COS Cells; D003545:Cysteine / Q000378:metabolism*; D051528:Guanylate Kinases; D051665:Kv1.4 Potassium Channel; D009154:Mutation; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011485:Protein Binding
chemical_list: D001704:Biopolymers; D051665:Kv1.4 Potassium Channel; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; D003545:Cysteine