Discrete limbal epithelial stem cell populations mediate corneal homeostasis and wound healing.

The accessibility and transparency of the cornea permit robust stem cell labeling and in vivo cell fate mapping. Limbal epithelial stem cells (LSCs) that renew the cornea are traditionally viewed as rare, slow-cycling cells that follow deterministic rules dictating their self-renewal or differentiation. Here, we combined single-cell RNA sequencing and advanced quantitative lineage tracing for in-depth analysis of the murine limbal epithelium.

Protein S Negatively Regulates Neural Stem Cell Self-Renewal through Bmi-1 Signaling.

Revealing the molecular mechanisms underlying neural stem cell self-renewal is a major goal toward understanding adult brain homeostasis. The self-renewing potential of neural stem and progenitor cells (NSPCs) must be tightly regulated to maintain brain homeostasis. We recently reported the expression of Protein S (PROS1) in adult hippocampal NSPCs, and revealed its role in regulation of NSPC quiescence and neuronal differentiation.

Protein S drives oral squamous cell carcinoma tumorigenicity through regulation of AXL.

The TAM family of proto-oncogenic receptor protein tyrosine kinases, comprising of TYRO3, AXL, and MERTK, is implicated in many human cancers. Their activation leads to cancer cell proliferation, enhanced migration, invasion, and drug resistance; however how TAMs are activated in cancers is less understood. We previously showed that Protein S (PROS1) is a ligand of the TAM receptors.

Targeted inhibition of WRN helicase, replication stress and cancer.

WRN helicase has several roles in genome maintenance, such as replication, base excision repair, recombination, DNA damage response and transcription. These processes are often found upregulated in human cancers, many of which display increased levels of WRN. Therefore, directed inhibition of this RecQ helicase could be beneficial to selective cancer therapy.

Protein S Regulates Neural Stem Cell Quiescence and Neurogenesis.

Neurons are continuously produced in brains of adult mammalian organisms throughout life-a process tightly regulated to ensure a balanced homeostasis. In the adult brain, quiescent Neural Stem Cells (NSCs) residing in distinct niches engage in proliferation, to self-renew and to give rise to differentiated neurons and astrocytes. The mechanisms governing the intricate regulation of NSC quiescence and neuronal differentiation are not completely understood.

Targeted inhibition of WRN helicase by external guide sequence and RNase P RNA.

Human WRN, a RecQ helicase encoded by the Werner syndrome gene, is implicated in genome maintenance, including replication, recombination, excision repair and DNA damage response. These genetic processes and expression of WRN are concomitantly upregulated in many types of cancers. Therefore, targeted destruction of this helicase could be useful for elimination of cancer cells.

Heparanase: one molecule with multiple functions in cancer progression.

Mammalian heparanase, an endoglycosidase-degrading heparan sulfate, is synthesized as a latent 65 kDa precursor that undergoes proteolytic processing, primarily by cathepsin-L, yielding 8 kDa and 50 kDa subunits that heterodimerize to form a highly active enzyme. Enhanced heparanase expression in human tumors correlates with metastatic potential, tumor vascularity, and reduced postoperative survival of cancer patients, attributed to enzymatic and nonenzymatic activities of the heparanase protein. Urinary and plasma levels of heparanase are elevated in cancer patients and suppressed in response to effective anticancer treatments.

Cathepsin L is responsible for processing and activation of proheparanase through multiple cleavages of a linker segment.

Heparanase is an endo-beta-d-glucuronidase that degrades heparan sulfate in the extracellular matrix and on the cell surface. Human proheparanase is produced as a latent protein of 543 amino acids whose activation involves excision of an internal linker segment (Ser(110)-Gln(157)), yielding the active heterodimer composed of 8- and 50-kDa subunits. Applying cathepsin L knock-out tissues and cultured fibroblasts, as well as cathepsin L gene silencing and overexpression strategies, we demonstrate, for the first time, that removal of the linker peptide and conversion of proheparanase into its active 8 + 50-kDa form is brought about predominantly by cathepsin L.

The impact of heparanese and heparin on cancer metastasis and angiogenesis.

Heparan sulfate (HS) proteoglycans play a key role in the self-assembly, insolubility and barrier properties of the extracellular matrix (ECM). Cleavage of HS therefore affects the integrity of tissues and hence normal and pathological phenomena involving cell migration and response to changes in the ECM. Mammalian heparanase, HS-degrading endoglycosidase,is synthesized as a latent 65 kDa precursor that undergoes proteolytic cleavage, yielding 8 kDa and 50 kDa subunits that heterodimerize to form a highly active enzyme.

Translocation of active heparanase to cell surface regulates degradation of extracellular matrix heparan sulfate upon transmigration of mature monocyte-derived dendritic cells.

After Ag capture and exposure to danger stimuli, maturing dendritic cells (DCs) migrate to regional lymph nodes, where antigenic peptides are presented to T lymphocytes. To migrate from peripheral tissue such as the epidermis to regional lymph nodes, Ag-bearing epidermal Langerhans cells must move through an extracellular matrix (ECM) of various compositions. The nature of their capacity to transmigrate via ECM is not well understood, although MIP-3beta and CCR7 play critical roles.

Site-directed mutagenesis, proteolytic cleavage, and activation of human proheparanase.

Heparanase is an endo-beta-D-glucuronidase that degrades heparan sulfate in the extracellular matrix and cell surfaces. Human proheparanase is produced as a latent 65-kDa polypeptide undergoing processing at two potential proteolytic cleavage sites, located at Glu109-Ser110 (site 1) and Gln157-Lys158 (site 2). Cleavage of proheparanase yields 8- and 50-kDa subunits that heterodimerize to form the active enzyme.