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Accumulating evidence during the last decades revealed that androgen can exert membrane initiated actions that involve signaling via specific kinases and the modulation of significant cellular processes, important for prostate cancer cell growth and metastasis. Results of the present work clearly show that androgens can specifically act at the membrane level via the GPCR oxoeicosanoid receptor 1 (OXER1) in prostate cancer cells. In fact, OXER1 expression parallels that of membrane androgen binding in prostate cancer cell lines and tumor specimens, while in silico docking simulation of OXER1 showed that testosterone could bind to OXER1 within the same grove as 5-OxoETE, the natural ligand of OXER1. Interestingly, testosterone antagonizes the effects of 5-oxoETE on specific signaling pathways and rapid effects such as actin cytoskeleton reorganization that ultimately can modulate cell migration and metastasis. These findings verify that membrane-acting androgens exert specific effects through an antagonistic interaction with OXER1. Additionally, this interaction between androgen and OXER1, which is an arachidonic acid metabolite receptor expressed in prostate cancer, provides a novel link between steroid and lipid actions and renders OXER1 as new player in the disease. These findings should be taken into account in the design of novel therapeutic approaches in prostate cancer.

Chlorobium tepidum is a Gram-negative bacterium of the green sulfur phylum (Chlorobia). Chlorobia are obligate anaerobic photolithoautotrophs that are widely distributed in aquatic environments where anoxic layers containing reduced sulfur compounds are exposed to light. The envelope of C. tepidum is a complex organelle composed of the outer membrane, the periplasm-peptidoglycan layer, and the cytoplasmic membrane. In addition to the outer and plasma membranes, C. tepidum contains chlorosomes attached to the cytoplasmic side of the plasma membrane. Each cellular compartment has a unique set of proteins, called sub-proteome. An important aim of proteome analysis is to study the level of the expressed genes and their response to environmental changes. Membrane protein studies are of primary importance to understand how nutrients are transported inside the cell, how toxic molecules are exported, and the mechanisms of photosynthesis and energy metabolism.

Chl. tepidum is a Gram-negative green-sulfur bacterium, which is strict by anaerobic and grows by utilizing sulfide or thiosulfate as an electron source. Blue native-polyacrylamide gel electrophoresis (BN-PAGE) is widely used for the analysis of oligomeric state and molecular mass non-dissociated protein complexes. In this study, a number of proteomic techniques were used to investigate the oligomeric state enzymes. In particular, the Chl. tepidum-soluble proteome was monitored under native condition by using BN-PAGE. The BN-PAGE protein complexes map was analyzed by MALDI-TOF MS after trypsin treatment and from 42 BN proteins bands, 62 different proteins were identified. Additionally, functional information regarding protein-protein interactions was assembled, by coupling 2-D BN-PAGE with MALDI-TOF MS. One-hundred and seventy gel bands were spotted, out of which 187 different proteins were identified. The identified proteins belong to various functional categories like energy metabolism, protein synthesis, amino acid biosynthesis, central intermediate metabolism, and biosynthesis of cofactors indicating the potential of the method for elucidation of functional proteomes.