This book is a printed edition of the Special Issue "Translocator Protein (TSPO)" that was published in IJMS

The high number of papers submitted and ultimately accepted for publication in this special issue attests the great amount of research being conducted on TSPO and its role in living cells. Thus, TSPO has become an extremely attractive subcellular biomark for the early detection of disease states overexpressing this protein and for the selective delivery to mitochondria of drugs and probes. Moreover, the effort in the design and synthesis of new, more specific and effective TSPO ligands proves to be very valuable. All these topics have been addressed in the special issue.

The 18 kDa translocator protein (TSPO) is an integral membrane protein known to be involved in porphyrin transport and heme biosynthesis. TSPO also plays a role in modulating immune response, regulation of cell proliferation and programmed cell death. TSPO is associated with several health conditions such as ischemic heart reperfusion, cancers and neurodegenerative diseases. While the potential of TSPO as a major therapeutic target has been well recognized, the lack of detailed understanding of its function and ligand binding sites have hindered drug design. In this thesis we will describe the expression, extraction and purification of Rhodobacter sphaeroides TSPO (RsTSPO). Rhodobacter is one of the closest ancestors of mitochondria and RsTSPO can be used as a model for mammalian TSPO. RsTSPO was overexpressed in E. coli, and it was extracted from the membranes with detergent (i.e. n-dodecylphosphocoline (DPC) and n-dodecyl-ß-D-maltoside (DDM)) then purified by Ni-affinity and size exclusion chromatographies. The RsTSPO could be expressed and purified in high yield (mg quantitites), high purity, and in its functional state. Binding studies of RsTSPO were performed utilizing fluorescence quenching of intrinsic tryptophans with a number of porphyrins ligands such as protoporphyrin IX (PPIX), hemin, meso-Tetra(4-sulfonatophenyl)porphine dihydrochloride (2HTPPS), Zn (II) meso-Terta(4-sulfonatophenyl)porphine dihydrochloride (ZnTPPS) and with the diagnostic ligand, PK11195. Binding studies of RsTSPO were performed in both detergents (DPC and DDM) to assess the effect of the membrane mimic environment on binding. We will also describe the first evidence of the catalytic activity of the purified RsTSPO under ambient light in the presence of molecular oxygen on its natural ligand, protoporphyrin IX. We will demonstrate the photodegradation of protoporphyrin IX by RsTSPO in the presence of oxygen and light. In addition, we have studied the effect of molecular oxygen and reactive oxygen scavengers (sodium azide and glutathione) on the decomposition of protoporphyrin IX. Also, we will describe preliminary NMR studies in an effort to characterize the ligand binding site(s) of TSPO. We have performed both solution and solid state NMR studies on pure RsTSPO and RsTSPO-ligand complexes.

Plant cells house highly dynamic cytoskeletal networks of microtubules and actin microfilaments. They constantly undergo remodeling to fulfill their roles in supporting cell division, enlargement, and differentiation. Following early studies on structural aspects of the networks, recent breakthroughs have connected them with more and more intracellular events essential for plant growth and development. Advanced technologies in cell biology (live-cell imaging in particular), molecular genetics, genomics, and proteomics have revolutionized this field of study. Stories summarized in this book may inspire enthusiastic scientists to pursue new directions toward understanding functions of the plant cytoskeleton. The Plant Cytoskeleton is divided into three sections: 1) Molecular Basis of the Plant Cytoskeleton; 2) Cytoskeletal Reorganization in Plant Cell Division; and 3) The Cytoskeleton in Plant Growth and Development. This book is aimed at serving as a resource for anyone who wishes to learn about the plant cytoskeleton beyond ordinary textbooks.

This is the fourth Special Issue in Pharmaceuticals within the last six years dealing with aspects of radiopharmaceutical sciences. It demonstrates the significant interest and increasing relevance to ameliorate nuclear medicine imaging with PET or SPECT, and also radiotherapeutical procedures.Numerous targets and mechanisms have been identified and have been under investigation over the previous years, covering many fields of medical and clinical research. This development is well illustrated by the articles in the present issue, including 13 original research papers and one review, covering a broad range of actual research topics in the field of radiopharmaceutical sciences.