Assessment of serum protein dynamics by native SILAC flooding (SILflood)

Turnover of blood serum proteins is a vital function in mammals, but technical challenges have thus far prevented comprehensive measurements of serum protein half-lives. Here, we injected native serum from heavy stable isotope labeled (SIL) mice into non-labeled recipients to quantify turnover of more than 200 proteins using mass spectrometry with high reproducibility and accuracy. We found a median of 19.4 h and a total range of 6-70 h for calculated half-lives. Moreover, we observed for proteins with equal function similar half-lives. To demonstrate the value and effectiveness of SILflood we investigated the impaired serum clearance in {beta}2-microglobulin (B2M-/-) deficient mice. Notably, we found that serum albumin and IgG half-lives were clearly reduced in B2M-/- animals compared to control animals. Taken together, our results demonstrate that SILflood is a versatile tool to investigate serum half-lives under regular and pathological conditions in living animals.