Increased CD36 protein as a response to defective insulin signaling in macrophages
J. Clin. Invest. Chien-Ping Liang, et al. 113:764 doi:10.1172/JCI19528 [Go to this article.]

Figure 5
The expression and signaling of insulin receptor is downregulated in ob/ob versus WT macrophages. (A) Insulin receptor β-subunit (IRβ) expression is decreased in pooled ob/ob compared with WT macrophages isolated from six mice of each strain, as determined by Western analysis. One experiment representative of three independent experiments is shown. A similar expression pattern is also found in ob/ob liver. (B and C) Insulin-dependent tyrosine phosphorylation of IR (B) and IRS-2 (C) in ob/ob macrophages is defective, even at a higher insulin concentration (10 nM) than ob/ob plasma insulin levels (about 4 nM). Ex vivo tyrosine phosphorylation of IR or IRS-2 by IR tyrosine kinase in response to insulin in ³²P-preincubated pooled ob/ob and WT macrophages isolated from five mice each was performed for 10 minutes. Total protein lysates were then subjected to immunoprecipitation with anti-IR or anti-phosphotyrosine (αP-Tyr) and separated by SDS-PAGE followed by membrane transfer and ³²P autoradiography. The membranes were then probed with anti–P-Tyr or anti-IR (for IR) or with anti–IRS-2, respectively. In C (bottom), P-Tyr p30 whose tyrosine phosphorylation status was not affected by insulin is shown to reflect the amounts of initial extracts used for immunoprecipitation of phosphoproteins. One experiment representative of two independent experiments is shown. IP, immunoprecipitation; IB, immunoblotting.