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Hydroxylated residues influence desensitization behaviour of recombinant α3 glycine receptor channels
Author(s) -
Breitinger HansGeorg,
Villmann Carmen,
Rennert Janine,
Ballhausen Diana,
Becker CordMichael
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2002.01109.x
Subject(s) - homomeric , desensitization (medicine) , biophysics , glycine receptor , receptor , chemistry , patch clamp , glycine , ion channel , homologous desensitization , protein subunit , hek 293 cells , biochemistry , amino acid , biology , gene
The human glycine receptor subunit α3 exists in two splice variants (α3K/L), with α3L bearing an additional segment of 15 amino acids within the cytoplasmic TM3‐4 loop. Homomeric α3K glycine receptors show faster desensitization than α3L receptors. Ion channel properties were compared of α3L, α3K, and of the triple mutant α3L ΔOH = α3L(T358A/Y367F/S370A), where hydroxyl functions of the spliced insert had been removed by site‐directed mutagenesis. Upon recombinant expression in HEK 293 cells, patch‐clamp recording experiments revealed that removal of hydroxyl functions primarily affected receptor desensitization. The fraction of non‐desensitizing current was 68 ± 13% for α3L, 21 ± 13% for α3K, and 48 ± 16% for α3L ΔOH . Desensitization time constants at saturating glycine concentration were 8.4 ± 2.8 s, 1.9 ± 2.3 s, and 2.8 ± 0.4 s, for α3L, α3K, and the triple mutant α3L ΔOH , respectively. In contrast, single‐channel and whole‐cell properties were similar for all three constructs. Thus, ion channel activation, desensitization, and conductance properties are independently controlled by distinct structural elements. Hydroxyl functions within the M3‐4 loop of the glycine receptor α3 subunit are crucial, but not exclusive, determinants of receptor desensitization.