Selenocysteine-Specific Mass Spectrometry Reveals Tissue-Distinct Selenoproteomes and Candidate Selenoproteins.

Selenoproteins, defined by the presence of selenocysteines (Sec), play important roles in a wide range of biological processes. All known selenoproteins are marked by the presence of Sec insertion sequence (SECIS) at their mRNA. The lack of an effective analytical method has hindered our ability to explore the selenoproteome and new selenoproteins beyond SECIS.

PI3K and STAT3: a new alliance.

Unlabelled: Recent proteomic data have uncovered an interdependence of PI3K and STAT3. In PI3K-tranformed murine cells, STAT3 is phosphorylated on Y705 and activated in a PI3K-dependent manner. Dominant negative STAT3 interferes with PI3K-induced oncogenic transformation.

Protein expression profiles of C3H 10T1/2 murine fibroblasts and of isogenic cells transformed by the H1047R mutant of phosphoinositide 3-kinase (PI3K).

We have used stable isotope labeling with amino acids in cell culture (SILAC) in conjunction with tandem mass spectrometry to characterize the proteomes of two isogenic cell lines that differ in the expression of a single oncoprotein,p110α of PI3K, carrying the H1047R mutation. 51,510 peptides were identified and assigned to 4,201 proteins. Most notable among the proteins that show increased expression in the oncogenically transformed cells are several involved in the interferon response including Isg15, Ifit1, Igtp and Oas2 (interferon stimulated gene 15, interferon-induced protein with tetratricopeptide repeats 1, interferon gamma-inducible GTP-binding protein, 2'-5'-oligoadenylate synthetase 2).

Phosphatidylinositol 4,5-bisphosphate-specific AKT1 is oncogenic.

The protein kinase AKT1 (v-akt murine thymoma viral oncogene homolog 1), also referred to as protein kinase B (PKB), is an essential mediator of the phosphatidylinositol 3-kinase signaling pathway. Elevated activity of AKT1 is common in human cancer. Localization at the plasma membrane, leading to enhanced phosphorylation and activation of AKT1, is an important factor determining the oncogenicity of this kinase.