Syntaxin4, P-cadherin, and CCAAT enhancer binding protein β as signaling elements in the novel differentiation pathway for cultured embryonic stem cells

A Cyclic Peptide Targets Glioblastoma by Binding to Aberrantly Exposed SNAP25

Disease-specific changes in tumors and other diseased tissues are an important target of research because they provide clues about the pathophysiology of the disease as well as uncover potentially useful markers for diagnosis and treatment. Here, we report a new cyclic peptide, CESPLLSEC (CES), that specifically accumulated (homed) in intracranial U87MG and the WT-GBM model of glioblastoma (GBM) from intravenous (IV) injection, and associated with the vasculature. Affinity chromatography of U87MG tumor extracts on insolubilized CES peptide identified Synaptosomal Associated Protein 25 (SNAP25) as a candidate target molecule (receptor) for CES. Several results supported the identification of SNAP25 as the CES receptor. IV-injected FAM-CES colocalized with SNAP25 in the tumors, and direct binding studies showed specific binding of the CES peptide to recombinant human SNAP25. A CES peptide-drug conjugate designed for photodynamic therapy showed selective cytotoxicity to SNAP25+ glioblastoma cell lines. Specific accumulation of systemically injected anti-SNAP25 antibody in U87MG glioblastoma and labeling of intact U87MG cells with anti-SNAP in flow cytometry showed that SNAP25 is available from the circulation but not in normal tissues and that it is present at the cell surface. Using an array of ECM proteins and surface plasmon resonance revealed that SNAP25 binds moderately to collagen V and strongly to collagen VI. Modeling studies suggested that CES and collagen VI compete for the same binding site on SNAP25. Our results introduce CES as a valuable targeting peptide for drug delivery and its receptor SNAP25 as a possible molecular marker of interest for glioblastoma.

CAMSAP3, a microtubule orientation regulator, plays a vital role in manifesting differentiation-dependent characteristics in keratinocytes

Microtubules constitute pivotal structural elements integral to cellular architecture and physiological functionality. Within the epidermis of the skin, microtubules undergo a noteworthy transition in orientation, shifting from centrosomal to non-centrosomal configurations during the processes of differentiation and stratification. This transition aligns with a discernible increase in the expression of CAMSAP3, a protein that binds to the minus end of microtubules, thereby regulating their orientation. In this study, we identified microtubule-bound CAMSAP3 within HaCaT keratinocytes, revealing an upregulation during the mitotic phase and accumulation at the intercellular bridge during cytokinesis. Building upon this observation, we scrutinized cellular responses upon a tetracycline/doxycycline-inducible CAMSAP3 expression in CAMSAP3-deficient HaCaT cells. Remarkably, CAMSAP3 deficiency induced shifts in microtubule orientation, resulting in cell cycle exit and delayed cytokinesis in a subset of the cells. Furthermore, our inquiry unveiled that CAMSAP3 deficiency adversely impacted the formation and stability of Adherens Junctions and Tight Junctions. In contrast, these perturbations were rectified upon the re-expression of CAMSAP3, underscoring the pivotal role of CAMSAP3 in manifesting differentiation-dependent characteristics in stratified keratinocytes. These observations emphasize the significance of CAMSAP3 in maintaining epidermal homeostasis.