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The protein p27 Kip1 plays roles that extend beyond cell-cycle regulation during cerebral cortex development, such as the regulation of neuronal migration and neurite branching via signaling pathways that converge on the actin and microtubule cytoskeletons. Microtubule-dependent transport is essential for the maturation of neurons and the establishment of neuronal connectivity though synapse formation and maintenance. Here, we show that p27 Kip1 controls the transport of vesicles and organelles along the axon of mice cortical projection neurons in vitro. Moreover, suppression of the p27 Kip1 ortholog, dacapo, in Drosophila melanogaster disrupts axonal transport in vivo, leading to the reduction of locomotor activity in third instar larvae and adult flies. At the molecular level, p27 Kip1 stabilizes the α-tubulin acetyltransferase 1, thereby promoting the acetylation of microtubules, a post-translational modification required for proper axonal transport., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Prosaposin is the precursor of four lysosomal activator molecules known as saposins A, B, C and D. It is also secreted and was proposed to be a neurotrophic factor. The neurotrophic function was attributed to the amino terminus of saposin C. In man, mouse and rat prosaposin is transcribed to two major isoforms differing in the inclusion of 9 bps of exon 8 within the saposin B domain. In the present study, we show that there is evolutionary conservation of the prosaposin structure and alternative splicing in chick and zebrafish as well. Moreover, there is conservation in prosaposin expression as tested immunohistochemically in the mouse and chick developing brain. We developed a sensitive assay to quantitate the prosaposin alternatively spliced forms. Our results indicate that, in mouse brain, skeletal and cardiac muscle the exon 8-containing RNA is most abundant, while it is almost absent from visceral and smooth muscle-containing organs. We observed temporal and differential expression of the alternatively spliced prosaposin mRNAs in mouse and chick brain as well as during development. The elevation in the abundance of exon 8-containing prosaposin RNA during mouse and chick brain development may suggest a role for the exon 8-containing prosaposin form in this process.

Breast cancer progression may be affected by various cellular components expressed by the tumor cells and/or by microenvironmental factors. Many studies report the correlation between breast cancer progression and monocyte infiltration into the tumor site. We have identified recently the CC chemokine regulated on activation, normal T cell expressed and secreted (RANTES), a major monocyte chemoattractant expressed by breast tumor cells, as a potential contributor to breast cancer progression. In the present study, analysis of the regulation of RANTES expression demonstrates that the expression of RANTES in breast tumor cells is elevated significantly and in a synergistic manner by IFN-gamma and tumor necrosis factor-alpha. Identification of the mechanisms by which RANTES may contribute to breast cancer progression included the analysis of the potential ability of RANTES to act in paracrine and indirect mechanisms, as well as directly on the tumor cells, to promote disease progression. Our results suggest that breast tumor cell-derived RANTES may promote breast cancer progression by its partial contribution to monocyte migration into breast tumor sites. Moreover, RANTES promotes the expression of matrix metalloproteinase (MMP) 9 by THP-1 monocytic cells and elevates vascularity in chick chorioallantoic membrane assays. Tumor necrosis factor-alpha, a major monocyte-derived cytokine, was found to promote the expression of MMP9 and MMP2 by MCF-7 and T47D breast adenocarcinoma cells, respectively, and to induce the de novo expression of an additional proteolytic enzyme by T47D cells, presumably MMP9. The possibility that RANTES may act directly on breast tumor cells was supported by detection of the expression of the CCR5 RANTES receptor in biopsy sections of breast cancer patients and by the ability of RANTES to promote the expression of MMP9 by MCF-7 cells. In all, our study suggests that the expression of RANTES by breast tumor cells results not only in monocyte migration to the tumor site but also in protumorigenic activities of RANTES and of proinflammatory cytokines that may facilitate metastasis formation and contribute to disease progression.