FIGURE 4.

Retardation of surfactant protein C (SFTPC)-I73T internalisation is not due to failed oligomerisation or ubiquitination. a) HeLa cells were transfected with haemagglutinin (HA)-tagged and green fluorescent protein (GFP)-tagged SFTPC (wild type (WT) or I73T) and lysates subjected to anti-GFP immunoprecipitation before immunoblotting for the HA tag and GFP. Both SFTPC-WT and SFTPC-I73T are equally able to oligomerise. b) Lysates from HeLa cells expressing SFTPC-WT or SFTPC-I73T were subjected to SFTPC immunoprecipitation and immunoblotted for ubiquitin. Note the presence of oligoubiquitinated SFTPC-WT (arrows) which is not seen in I73T-expressing cells. c) Quantitative SFTPC internalisation assay of cells expressing GFP-SFTPC-WT, I73T or K6R. n=3. Data are presented as mean±sem.