Figure 4.

PS1 stimulates Ca²⁺-dependent cell–cell aggregation. (A) Nontransfected (−E-cad) PS1 +/+ (+/+) or E-cadherin-transfected (+E-cad) PS1 +/+ (+/+) and PS1−/− (−/−) fibroblasts were allowed to aggregate for 4 h in the presence (+Ca²⁺) or absence (−Ca²⁺) of calcium (see Materials and Methods). (B) E-cadherin-expressing PS1−/− fibroblasts, transiently transfected with vector (Vector), WT PS1 (wtPS1), or PS1 FAD mutant ΔE9 (PS1ΔE9), were assayed for aggregation in the presence or absence of calcium. (Right) Extracts (1% Triton X-100) from the transiently transfected cultures shown in B were treated with antibody 33B10, and the resulting IPs (PS1/CTF IP) were analyzed for expression of the transfected PS1 proteins.