SNAP-25 a membrane-associated protein of the nerve terminal, is specifically cleaved by botulinurn neurotoxins serotypes A and E, which cause human and animal botulism by blocking neurotransmitter release at the neuromuscular junction. Here we show that these two metallo-endopeptidase toxins cleave SNAP-25 at two distinct carboxyl-terminal sites. Serotype A catalyses the hydrolysis of the Gln'97-Arg'98 peptide bond, while serotype E cleaves the Arg'80-Ile'8' peptide linkage. These results indicate that the carboxyl-terminal region of SNAP-25 plays a crucial role in the multi-protein complex that mediates vesicle docking and fusion at the nerve terminal.

Background

The aim of the present study was to demonstrate the mitogenic and differentiating properties of platelet-rich plasma releasates (PRPr) on human chondrocytes in mono- and three-dimensional cultures. In order to assess if PRPr supplementation could maintain the chondrocyte phenotype or at least inhibit the cell de-differentiation even after several days in culture, we performed a proteomic study on several cell cultures independently grown, for different periods of time, in culture medium with FCS, human serum (HS), and releasates obtained from PRP and platelet-poor plasma (PPP). We found that PRP treatment actually induced in chondrocytes the expression of proteins (some of which novel) involved in differentiation.

NELL‐1 (Nel‐like molecule‐1) is a secreted osteogenic growth factor first identified in human craniosynostosis (CS) patients. NELL‐1 protein has been observed to promote bone and cartilage differentiation and to suppress adipogenesis in both in vitro and in vivo models. Despite these findings, the cell surface receptors of NELL‐1 have remained unknown. In this study, we observed for the first time that NELL‐1 promotes cell adherence in multiple cell lines, including ST2, C3H10T1/2, M2‐10B4, ATDC5, and MC3T3 cells. Additionally, we found that NELL‐1 binds to extracellular Integrinβ1 and induces cell focal adhesion. By utilizing siRNA methods, we determined that NELL‐1 cell surface binding and enhanced cell attachment were dependent on Integrinβ1 expression. Finally, we observed that pre‐coating of culture dishes or PLGA (polylactic‐co‐glycolic acid) scaffold with NELL‐1 resulted in a significant increase in both cell attachment and osteogenic differentiation. Our results identify for the first time a cell surface target of NELL‐1, Integrinβ1, and elucidate new functions of NELL‐1 in promoting cell adherence and osteogenic differentiation. J. Cell. Biochem. 113: 3620–3628, 2012. © 2012 Wiley Periodicals, Inc.

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