A) GROWING AND LABELLING CELLS.
1. Grow cells of interest to 80% confluence in 100 mm dishes. Serum starve overnight in media containing 0.5% BSA (insulin-free), no serum, if you are going to stimulate.
2. Make media: take phosphate-, methionine- free (RPMI) media and add 32 mg anhydrous Na2HPO4 per 40 mls of media. Sterile filter.
3. In hood, remove media, wash once with methionine-free media, and add 5 ml of methionine-free media containing 0.5-1.0 mCi 35S-methionine (Amersham TranSlabel) per plate. Place in incubator overnight to label to equilibrium. (STERILE). Also place a large weigh boat of activated charcoal in the incubator to adsorb 35SO4.
4. Stimulate cells for the desired time with the appropriate concentration of the desired growth factor (e.g. 1 min with 50 ul of 10-5 M insulin (for 10-7 M final)).
5. Aspirate media quickly (hot waste), freeze cells by dousing in liquid nitrogen. Pour off excess LN2, add 1 ml/plate of solubilization buffer:
50 mM HEPES pH 7.4
1.0% Triton X-100 500 ul
2 mM Vanadate 18 mg
2 mM PMSF 500 ul of stock (35 mg/ml EtOH)
NaF 210 mg
5 mM EDTA 500 ul of 0.5 M stock
5. Thaw cells into buffer, scrape with cell lifter, transfer to polycarbonate centrifuge tubes with caps and spin in Ti70 rotor 55 krpm for 1 hour.
6. Immunoprecipitate supernatant with (20ul) of desired antibody (2 hr-overnight), collect on 100 ul pansorbin 1+ hours. Re-immunoprecipitate if desired.
7. Collect pellets-- spin down, aspirate supernatant (hot waste). Add 1 ml Tris-SDS IP wash, sonicate. Repeat 2 additional times. Aspirate supernatant, add 70 ul of laemmli sample buffer.
8. Boil 5', vortex to resuspend pellet, boil 3'. Spin down pansorbin 5', load supernatant to gel.