Neuroproteomics in stem cell differentiation.

The term "proteome" is used to describe the entire complement of proteins in a given organism or in a system at a given time. Proteome analysis in neuroscience, also called "neuroproteomics" or "neuromics" is in its initial stage, and shows a deficit of studies in the context of brain development. It is the main objective of this review to illustrate the potential of neuroproteomics as a tool to unravel the differentiation of neural stem or progenitor cells to terminally differentiated neurons. Experimental results regarding the rat striatal progenitor model cell line ST14A are presented to illustrate the large rearrangements of the proteome during the differentiation process of neural progenitor cells and their modification by neurotrophic factors like the glial cell line-derived neurotrophic factor (GDNF). Thereby native stem cells and cells transfected with GDNF gene were investigated at the proliferative state and at seven time points up to 72 h after induction of differentiation. In addition, the immortalized human fetal midbrain stem cell line ReNcell VM was analyzed in order to detect stem cell differentiation associated changes of the protein profile. This review gives also an outlook on technical improvements and perspectives of application of neural stem cell proteomics.

Analysis of photosynthetic complexes from a cyanobacterial ycf37 mutant.

The Ycf37 protein has been suggested to be involved in the biogenesis and/or stability of the cyanobacterial photosystem I (PSI). With Ycf37 specific antibodies, we analyzed the localization of Ycf37 within the thylakoid membranes of the cyanobacterium Synechocystis sp. PCC 6803. Inspection of a sucrose gradient profile indicated that small amounts of Ycf37 co-fractionated with monomeric photosynthetic complexes, but not with trimeric PSI. Isolating 3xFLAG epitope-tagged Ycf37 by affinity-tag purification rendered several PSI subunits that specifically co-precipitated with this protein. Blue-native PAGE newly revealed two monomeric PSI complexes (PSI and PSI*) in wild-type thylakoids. The lower amount of PsaK present in PSI* may explain its higher electrophoretic mobility. PSI* was more prominent in high-light grown cells and interestingly proved absent in the Deltaycf37 mutant. PSI* appeared again when the mutant was complemented in trans with the wild-type ycf37 gene. In the Deltaycf37 mutant the amount of trimeric PSI complexes was reduced to about 70% of the wild-type level with no significant changes in photochemical activity and subunit composition of the remaining photosystems. Our results indicate that Ycf37 plays a specific role in the preservation of PSI* and the biogenesis of PSI trimers.