FIGURE 4.
14-3-3 proteins modulate the kinetics of homomeric GluK2a receptors in a heterologous system. A and B, GluK2a current traces are evoked by glutamate (1 mm, 100 ms) in outside-out configuration from HEK293 cells cotransfected with KAR subunits and other proteins as indicated. Desensitization time constants (τdes) are determined by single exponential fits to the decaying phase of the currents. A, representative current traces recorded from outside-out patches in HEK293 cells transfected with GluK2a subunits, together with either corresponding vector (dark trace), 14-3-3τ (red trace), pSCM138 (green trace), or pSCM174 (blue trace). Cotransfection of pSCM138, but not pSCM174, significantly accelerates the desensitization of homomeric GluK2a receptors, whereas cotransfection 14-3-3τ significantly slows the desensitization of homomeric GluK2a receptors. Right panel summarizing group data for vector (n = 12), 14-3-3τ (n = 10), pSCM138 (n = 9), and pSCM174 (n = 11) cotransfected cells. Data represent mean ± S.E., *, p < 0.05; ***, p < 0.001. B, representative current traces from outside-out patches in HEK293 cells transfected with the 14-3-3-binding deficient mutant 4SA-GluK2a, together with either the vector (dark trace) or 14-3-3τ (red trace). Desensitization of the mutant GluK2a receptor is not affected by coexpressed 14-3-3τ. Right panel shows the summary data (n = 10 and 9 for without and with 14-3-3τ, respectively). C, representative currents evoked by either 0.3 or 3 mm glutamate on outside-out patches from HEK293 cells transfected with GluK2a subunits, together with either corresponding vector (dark trace) or 14-3-3τ (red trace). Cotransfection of 14-3-3τ slows the desensitization of homomeric GluK2a currents evoked by low (0.3 mm) but not the high (3 mm) concentration of glutamate. Right panel shows the summary data (0.3 mm group, n = 11 and 9; 1 mm group, n = 12 and 10; 3 mm group, n = 16 and 15 for without and with 14-3-3τ, respectively). Data represent mean ± S.E., **, p < 0.01; ***, p < 0.001.