Fig. 3
p300/CBP Promotes Tau Secretion a–c p300 overexpression in HEK293T cells increases tau secretion. a Representative immunoblot of total tau (t-tau), phosphor-tau (p-tau, AT8), acetylated tau (ac-tau, K174), and GAPDH in the lysate (5% of total) and conditioned medium (25% of total) of HEK293T cells transfected with tau alone or tau+p300. HEK293T cells were serum-starved for 48 h after transfection. The conditioned medium was concentrated 25-fold. b, c Quantification of intracellular total tau (t-tau) levels (b) and t-tau secretion (c), normalized to control. t-tau secretion was quantified by normalizing extracellular tau to intracellular tau. n = 8 wells from eight independent experiments. *p < 0.05, **p < 0.01 by unpaired t test. d–g p300/CBP double knockout in primary mouse neurons reduces tau secretion. d Representative immunoblot of ac-tau (K174), t-tau, and GAPDH in the lysate of p300F/F/CBPF/F primary neurons infected with lenti-ctrl or lenti-Cre. e hTau mRNA levels in p300F/F/CBPF/F primary neurons infected with lenti-ctrl or lenti-Cre, by qRT-PCR. n = 4 wells from two independent experiments. ns, non-significant by unpaired t test. f Quantification of intracellular t-tau levels by tau ELISA, normalized to control. g Quantification of tau secretion over 3 h by ELISA, normalized to intracellular tau levels and normalized to control. n = 6 wells from three independent experiments. **p < 0.01, ***p < 0.001, unpaired t test. h, i CTB treatment increase tau secretion in primary mouse neurons. h Quantification of intracellular total tau levels by tau ELISA, normalized to control. i Quantification of tau secretion over 3 h by ELISA, normalized to intracellular tau levels and normalized to control. n = 8 wells from four independent experiments. *p < 0.05, **p < 0.01, unpaired t test. Values are mean ± SEM