Viral vectors as part of an integrated functional genomics program

Differentiation of a human neuroblastoma into neuron-like cells increases their susceptibility to transduction by herpesviral vectors

Gene transfer is a powerful tool for functional gene analysis in human cells. In this respect, there is a need to develop experimental models that involve homogeneous cultures of human neuron-like cells susceptible to gene transduction and that are easy to handle. Here we describe an optimized and reproducible procedure to differentiate human SH-SY5Y neuroblastoma cells into a homogeneous population of neuron-like cells. The fully differentiated cells are postmitotic and resemble primary cultured neurons in terms of their cytoskeletal polarity. Notably, differentiated SH-SY5Y cells are far more susceptible to transduction by herpes simplex virus (HSV-1)-based vectors than proliferating SH-SY5Y cells. This increase in transduction efficiency after neuronal differentiation may be due to the up-regulation of cell surface receptors for herpesvirus entry. In summary, we propose that fully differentiated human neuron-like cells obtained from the SH-SY5Y neuroblastoma may constitute an excellent and versatile experimental tool for gene transfer and functional genomic studies with HSV-1 vectors.

The tetraspan protein epithelial membrane protein-2 interacts with beta1 integrins and regulates adhesion

The growth arrest-specific-3 (GAS3)/PMP22 proteins are members of the four-transmembrane (tetraspan) superfamily. Although the function of these proteins is poorly understood, GAS3/PMP22 proteins have been implicated in the control of growth and progression of certain cancers. Epithelial membrane protein-2 (EMP2), a GAS3/PMP22 family member, was recently identified as a putative tumor suppressor gene. Here, we addressed the normal function of EMP2 by testing the prediction that it influences integrin-related cell functions. We observed that EMP2 associates with the beta(1) integrin subunit. Co-immunoprecipitation and immunodepletion experiments indicated that approximately 60% of beta(1) integrins and EMP2 can be isolated in common protein complexes. Whereas this association between EMP2 and beta(1) integrin may be direct or indirect, it has features of integrin heterodimer selectivity. Thus, by laser confocal microscopy, EMP2 colocalized with alpha(6)beta(1) but not alpha(5)beta(1) integrin. Increased expression of EMP2 also influenced the integrin heterodimer repertoire present on the plasma membrane. EMP2 specifically increased the surface expression of the alpha(6)beta(1) integrin while decreasing that of the alpha(5)beta(1) protein. Reciprocally, reduction in EMP2 expression using a specific ribozyme decreased surface expression of alpha(6)beta(1) integrin. Accordingly, these EMP2-mediated changes resulted in a dramatic alteration in cellular adhesion to extracellular matrix proteins. This study demonstrates for the first time the interaction of a GAS3/PMP22 family member with an integrin protein and suggests that such interactions and their functional consequences are a physiologic role of GAS3/PMP22 proteins.