Figure 3.

Spry inhibits inositol phosphate (IP) production after receptor stimulation. (A) NIH 3T3 cells cultured in the presence of [³H]inositol were serum starved and stimulated with PDGF BB (20 ng/ml) for increasing periods in the presence or absence of doxycycline (Dox) to induce Spry1 expression. Lipids were collected from the cell lysates, and radiolabeled IPs were fractionated and counted by liquid scintillation. Inositol phosphate levels are expressed as a percentage of total radioactive inositol incorporation. (B) Spry1,2,4 null or control adenovirus-GFP fibroblasts were serum starved and treated with PDGF BB (20 ng/ml) for the indicated times and assayed for IPs. (C) A bone marrow mast cell line derived from a wild-type or Spry2^−/− mouse was treated with IgE followed by dinitrophenol-human serum albumin to cross-link Fc receptors. Cell lysates were prepared at the indicated times and assayed for IPs. All experiments were performed three times (see Supplemental Table 1, A–C) with similar results obtained.