Figure 2.

Ubiquitination of AQP1. (A) Fibroblasts were incubated in control medium or in the presence of proteasome inhibitors (MG132, lactacystin) for 8 h, and protein immunoblots of total cell lysates were probed with anti-ubiquitin antibodies. (B) Fibroblasts were incubated in control medium or with proteasome inhibitors, and AQP1 was immunoprecipitated. Rabbit IgG was used as the immunoprecipitation control. Immunoblots were probed with anti-ubiquitin antibodies. Arrowheads mark the position of discrete bands from approximately 44 to 65 kDa, consistent with addition of different numbers of ubiquitin moieties (approximately 7.5–8 kDa per ubiquitin) to the 28-kDa AQP1 monomer, beginning with an ubiquitin dimer at the lowest arrowhead. The bracket denotes higher molecular mass ubiquitinated products.