Cover Picture: Proteomics 13'09

AbstractHuman Growth Hormone: Variants vary in sugar coatingIn the last issue we commented on the age and variants of the heat shock proteins, in this issue we take a brief look at another old family with connections, the growth hormones. Human growth hormone (hGH) is produced in at least eight different flavors and two different tissues with apparent molecular weights ranging from 5 to 45 kDa, from anterior pituitary and placenta. Functional roles include growth promotion and insulin potentiation. Bustamante et al. characterized the structure of the O‐linked oligosaccharide they had found earlier attached to hGH‐24. The study required ESI‐ and MALDI TOF‐MS/MS, and high‐performance anion exchange chromatography with pulsed amperometric detection to determine the point of attachment and carbohydrate branching structure. A theoretical 3‐D model placed the carbohydrate in the hGH‐24 high affinity binding site 1.Bustamante, J. et al., Proteomics 2009, 9, 3474–3488.Phospho‐tyrosine targets: T‐ and B‐cell receptor activationPhosphorylation at serine, threonine or tyrosine is one of the most common post‐translational modifications of eukaryotic proteins. The response of genetically similar proteins to phosphorylation is distinct and separate. Matsumoto et al. report here a catalog of the upstream and downstream effects of the phosphorylation of tyrosine in T‐cell (Jurkat cell line, TCR) and B‐cell (Namalwa cell line, BCR) receptors. Proteins were identified by SDS‐PAGE followed by in‐gel digestion, LC and MS/MS. Tyrosine phosphorylated proteins were selectively enriched using an immunoaffinity approach while quantitative aspects were determined by SILAC (stable isotope labeling in cell culture). Status of the receptor endocytosis machinery was checked. A total of 1243 proteins were identified. Alternative criteria yielded 725 proteins and 128 of those were found under all conditions. Many known proteins were found and an interesting new one – PLCγ1 was phosphorylated in Jurkat but not Namalwa cells, PLCγ2 was the reverse.Matsumoto, M. et al., Proteomics 2009, 9, 3549–3563.Tipsy PIPs lose grip on proteasomesProteasomes are the principal “protein garbage eaters” of the eukaryotic cell. The core is a 20S, 28 subunit complex, which is assembled with other subunits for various purposes, including immune clean‐up in response to interferon release, destruction of ubiquitin‐tagged proteins and short‐lived or misfolded proteins. It also has regulatory functions, controlling cell cycles, hypoxic response and transcription. Chronic alcohol ingestion causes severe damage to rat and human liver. Bousquet‐Dubouch et al. report on facets of the proteasome affected by chronic ethanol administration (at ≥2×human drunk driving limit in many US states) for a month. After careful nondenaturing isolation of proteasomes from drunk and sober rats, they identified proteasome interacting proteins (PIPs) by nanoLC‐ESI‐QTOF‐MS/MS and quantitated by Western blots and ICAT techniques. A number of ubiquitin‐associated proteins were downregulated, one was missing, as was a stabilizer of 20S‐activator complexes.Bousquet‐Dubouch, M.‐P. et al., Proteomics 2009, 9, 3609–3622.