Metabolic labeling with fatty acids

S-acylation of Ca2+ transport proteins in cancer

Alterations in cellular calcium (Ca2+) signals have been causally associated with the development and progression of human cancers. Cellular Ca2+ signals are generated by channels, pumps, and exchangers that move Ca2+ ions across membranes and are decoded by effector proteins in the cytosol or in organelles. S-acylation, the reversible addition of 16-carbon fatty acids to proteins, modulates the activity of Ca2+ transporters by altering their affinity for lipids, and enzymes mediating this reversible post-translational modification have also been linked to several types of cancers. Here, we compile studies reporting an association between Ca2+ transporters or S-acylation enzymes with specific cancers, as well as studies reporting or predicting the S-acylation of Ca2+ transporters. We then discuss the potential role of S-acylation in the oncogenic potential of a subset of Ca2+ transport proteins involved in cancer.

Regulation of Cell Polarity by Posttranslational Protein Palmitoylation

Cell polarity is a common feature of many living cells, especially epithelial cells, and plays important roles in development, tissue homeostasis, and diseases. Therefore, the signaling pathways involved in establishing and maintaining cell polarity are tightly controlled. Protein S-palmitoylation has been recently recognized as an important posttranslational modification involved in cell polarity, via dynamic covalent attachment of fatty acyl groups to the cysteine residues of cell polarity proteins. Here, we describe the methods to study the function and regulation of S-palmitoylation of cell polarity proteins.

Analysis of protein S-acylation by gas chromatography-coupled mass spectrometry using purified proteins

S-acylation, also known as palmitoylation, involves the attachment of acyl fatty acids to thiol groups of cysteine residues through a reversible thioester bond. Owing to its reversibility, S-acylation is important in regulation of diverse signaling cascades, including Ras-associated cancers in mammals, stress response and metabolic regulation. Here we describe a simple protocol for analysis of protein S-acylation using gas chromatography-coupled mass spectrometry. Analysis can be carried out with as little as 1 microg of purified protein and allows chemical identification and, potentially, quantification of the acyl moieties. The method is based on cleavage of the fatty acids from proteins by hydrogenation with platinum (IV) oxide. This causes an acid transesterification of the acyl groups, adding an ethyl group to the carboxyl head of the fatty acid. The addition of the ethyl group reduces the polarity of the fatty acids, allowing their efficient separation by gas chromatography.