HTN1

Hst 1 functions primarily as a wound healing factor by activating cell-surface and cell-cell adhesions, cell spreading and migration and it can also stimulate cellular metabolic activity (PubMed:18650243, PubMed:25903106, PubMed:28542418, PubMed:28751526, PubMed:32225006, PubMed:35970844). Hst 1 is internalized in host cells in a stereospecific and energy-dependent process, which is partially mediated by the G protein-coupled receptors (GPCR)-activated endocytosis (PubMed:35970844). Internalized Hst 1 is targeted and released via early endosomes trafficking to the mitochondria, where it significantly enhances mitochondrial energy metabolism (PubMed:32225006, PubMed:35970844). At the mitochondria, Hst 1 increases mitochondria-ER contacts through binding with ER receptor TMEM97, which also stimulates metabolic activity and cell migration and may as well regulate calcium homeostasis of the cell (PubMed:32225006, PubMed:34233061, PubMed:35970844). Also activates the ERK1/2 signaling pathway to promote cell migration, possibly upon interaction with GPRCs at the plasma membrane (PubMed:28751526). Also triggers the RIN2/Rab5/Rac1 signaling cascade which activates endothelial cell adhesion, spreading and migration required for angiogenesis in the oral wound healing process, however the receptor that transduces Hst 1 signal has not yet been identified (PubMed:28751526). Also displays antimicrobial functions against pathogenic yeast Candida albicans, although with less effectiveness than Hst 5 (PubMed:28751526, PubMed:3286634, PubMed:3944083). Hst 2 consists of the fragment sequence 12-28 of Hst 1. Similar to Hst 1, actively and stereospecifically internalized in host cells and targeted to the mitochondria and the ER and promotes cell metabolic activity (PubMed:18650243, PubMed:32225006). Also activates the ERK1/2 signaling pathway to promote cell migration and wound closure (PubMed:18650243). In contrast with Hst 1, not able to promote cell-substrate and cell-cell adhesion (PubMed:25903106). Histatins (Hsts) are cationic and histidine-rich secreted peptides mainly synthesized by saliva glands of humans and higher primates (PubMed:3286634, PubMed:3944083). Hsts are considered to be major precursors of the protective proteinaceous structure on tooth surfaces (enamel pellicle). Hsts can be divided into two major groups according to their biological functions: antimicrobial Hsts (e.g. Hst 5/HTN3) and cell-activating Hsts (e.g. Hst 1/HTN1 and Hst 2/HTN1) (PubMed:32225006). Hst 1/HTN1 and Hst 2/HTN1 act in different cell types (epithelium, fibroblasts and endothelium) in oral and non-oral mucosa (PubMed:25903106, PubMed:28542418, PubMed:28751526, PubMed:32225006).