Previously, we have shown that pinin/DRS (Pnn), a 140-kDa nuclear and cell adhesion-related phosphoprotein, is involved in the regulation of cell adhesion and modulation of the activity of multiple tumor suppressor genes. In the nucleus Pnn is concentrated in the "nuclear speckles," zones of accumulation of transcriptional and mRNA splicing factors, where Pnn is involved in mRNA processing. Alternatively, other roles of Pnn in gene regulation have not yet been established. By utilizing in vitro pull-down assays, in vivo interaction studies, and immunofluorescence in combination with overexpression and RNA interference experiments, we present evidence that Pnn interacts with the known transcriptional corepressor CtBP1. As a consequence of this interaction Pnn was capable of relieving the CtBP1-mediated repression of E-cadherin promoter activity. Our results suggest that the interaction of Pnn with the corepressor CtBP1 may modulate repression of transcription by CtBP1. This interaction may reflect the existence of coupling factors involved in CtBP-mediated transcriptional regulation and mRNA processing events.We studied a molecule, pinin (Pnn/DRS/memA), a 140-kDa phosphoprotein associated with the desmosome and localized in the nucleus of various tissues and cultured cell lines (4, 40-42, 52, 53, 62), which seems to play a key role in the establishment and maintenance of epithelia (53, 56). The expression of exogenous Pnn in transformed cells dramatically altered the recipient cells' morphology, driving them to a more epithelial phenotype. Expression of Pnn was linked to the expression of genes such as E-cadherin, p21 cip/waf , MIC-1, and Rho-A, which impact epithelial adhesion, proliferation, and cell motility (55). These observations suggest that Pnn may play an integral role in epithelial-cell-specific gene expression.Transfection experiments revealed that the majority of expressed Pnn is found within the nucleus, exhibiting a diffuse nucleoplasmic and nuclear speckle distribution. However, little, if any, exogenous Pnn was localized to cell-cell adhesion sites. This raises the possibility that Pnn may be exerting its effect predominantly via interaction with nuclear components, perhaps involving mRNA transcription and processing (48,62). The proposed functions of nuclear speckles include a role as storage compartments for molecular components involved in gene transcription, such as a subpopulation of polymerase II, and mRNA processing machinery, such as the SR family of proteins. SR proteins distinguished by their serine/argininerich motifs are required for constitutive mRNA splicing and regulation of alternative splice site selection (6,30,36,37,47,58). Previous two-hybrid and colocalization experiments revealed that Pnn indeed binds to, and colocalizes with, the SR protein family members SRp75 and SRm300, known components of the spliceosome machinery, and a novel SR protein (9,47,62,65). In addition, Pnn was demonstrated to contribute to the alternative splice site selection in splicing reporter assays, sp...

The results suggest that Pnn and SR-rich proteins may be part of a multiprotein complex within the nucleus and may be involved in pre-mRNA processing.

Our data suggest that in vivo CSLO imaging of EYFP-RGC expression and SD-OCT measured NFL thickness are fast and reliable methods that longitudinally track neurodegenerative progression following ONC injury. Neurodegenerative changes in NFL thickness measured by SD-OCT imaging have the same overall trajectory as those observed by CSLO for RCD; however, changes in NFL thickness initially lag behind in vivo RGC soma counts with a slower decline in overall measurable change.