Figure 7.

Plasma membrane recruitment of Sec3 is temporally distinct from that of Sec6 and Sec8. Low-density cultures of contact-naïve MDCK cells were seeded in LCM on collagen-coated coverslips and incubated for 2 h (A and C) or for 1 h, before shifting them to HCM for 1 h (B). (A) Cells were fixed and colabeled with anti-Sec3CT and anti-Sec6(9H5), anti-Sec8(8F12), or anti-E-cadherin antibodies. Note that within 2 h in LCM, E-cadherin, Sec6, and Sec8 were enriched at sites of cell–cell contact, but Sec3 was not recruited to plasma membranes under these conditions. (B) Cells were fixed and colabeled with anti-Sec3CT and anti-Sec6(9H5) or anti-E-cadherin antibodies. Under these culture conditions, Sec3 was observed to accumulate at sites of cell-cell contact. (C) Cells were fixed and colabeled with anti-Sec3CT and anti-Dsc2/3 antibodies. Note that cytoplasmic puncta of Sec3 colocalize with this desmosomal cadherin in contact-naïve cells.