Kisspeptin-10

The KISS1 gene was first described by Lee et al. (1996) as a human malignant melanoma metastasis-suppressor gene mapped to chromosome 1q32. Microcell-mediated chromosome 6 transfer into melanoma cell lines demonstrated that metastatic capacity is a phenotype separable from tumor formation. The gene product was subsequently shown to be the precursor of an endogenous peptide ligand. In 2001, three groups independently identified GPR54 and its ligands: Ohtaki et al. (2001) isolated a 54–amino-acid carboxy-terminally amidated peptide from human placenta as the endogenous ligand of GPR54; Kotani et al. (2001) characterized the KISS1-derived kisspeptins — including KP-54, KP-13, and KP-10 — as natural GPR54 ligands with documented binding and functional activity; and Muir et al. (2001) cloned the human receptor (designated AXOR12) and identified KISS1-derived peptides as its agonists. These studies established KP-10 (the C-terminal decapeptide, corresponding to PubChem CID 25240297, formula C63H83N17O14, sequence YNWNSFGLRF-amide) as the minimal active fragment, retaining full intrinsic activity relative to the longer kisspeptin forms.

A second wave of research established the kisspeptin/GPR54 system as a central gatekeeper of the reproductive axis. Two 2003 human genetics studies — Seminara et al. (2003, New England Journal of Medicine) and de Roux et al. (2003, PNAS) — independently reported that loss-of-function mutations in GPR54/KISS1R are associated with idiopathic hypogonadotropic hypogonadism and absent puberty, a phenotype reproduced in GPR54-null mice. This work reframed the system from a metastasis-suppressor pathway into a master regulator of puberty and fertility. Gottsch et al. (2004) administered KP-54 and KP-10 to mice and examined gonadotropin secretion in that context. Messager et al. (2005) demonstrated that kisspeptin acts directly on GnRH neurons via GPR54 to stimulate GnRH release, with no response in GPR54-null mice, establishing the direct neural circuit through which KP-10 is studied. The comprehensive review by Pinilla et al. (2012, Physiological Reviews) consolidated the molecular features and regulatory mechanisms of kisspeptins in HPG axis biology.

KP-10 has been used as a probe of pubertal axis activation. Shahab et al. (2005, PNAS) administered kisspeptin-10 to agonadal juvenile male rhesus monkeys and measured the GnRH/LH response, while characterizing developmental changes in hypothalamic KISS1 and GPR54 mRNA across the peripubertal period. Roseweir et al. (2009, Journal of Neuroscience) engineered amino-substituted analogues of kisspeptin-10 to develop kisspeptin antagonists as pharmacological tools, which were then used to delineate the role of kisspeptin neurons in GnRH secretion in mouse and pubertal monkey models. These studies used KP-10 both as an agonist reference and as the structural scaffold from which pharmacological tools were derived.

KP-10 serves as the principal ligand in KISS1R pharmacology studies. Kotani et al. (2001) documented Gq/11–PLC coupling, calcium mobilization, arachidonic acid release, and ERK1/2 and p38 MAP kinase phosphorylation in GPR54-transfected cell systems. Structure-activity studies — including Tomita et al. (2006, Bioorganic & Medicinal Chemistry) examining C-terminal pentapeptide analogues — characterized the structural requirements for GPR54 agonism, identifying the C-terminal RF-amide, Phe6, Arg9, and Phe10 as residues critical for receptor engagement. NMR and membrane-mimetic studies characterized the conformation of KP-10 in lipid micelles, describing turn structures spanning the Trp3-to-Phe10 segment and examining the relationship between membrane binding and agonist activity.

Cryo-EM structural studies have resolved the molecular basis of kisspeptin receptor ligand recognition. Shen et al. (2024, Cell Reports) reported Gq-coupled KISS1R bound to kisspeptin-10 and to a synthetic analog, defining a three-segment binding mode in which N-terminal residues (YNWNSF) sit between the extracellular loops and the C-terminal RF-amide inserts into the transmembrane core (PDB 8ZJD). A distinctive orientation of the receptor's intracellular TM6 region relative to other Gq-coupled receptors was noted. Wu et al. (2024, Science Advances) resolved KISS1R–Gq and KISS1R–Gi complexes, demonstrating that the receptor can couple to the Gi/o pathway in addition to the canonical Gq/11 pathway. Together these structures provide an atomic-level framework for analyzing kisspeptin analog engagement at the receptor.

The original KISS1 gene discovery established the system in cancer biology. Ohtaki et al. (2001) examined chemotaxis and invasion of GPR54-transfected CHO cells in vitro and assessed pulmonary metastasis in a GPR54-transfected mouse melanoma model. KP-10 has since been used in tumor-cell model systems — including melanoma, breast, pancreatic, endometrial, and thyroid cell lines — to study chemotaxis, adhesion, invasion, and CXCR4/SDF-1 signaling. Bilban et al. (2004, Journal of Cell Science) used KP-10 in primary human trophoblast models, examining invasion in the context of placental biology.

KP-10 has been examined in registered human reproductive physiology studies. George et al. (2011, Journal of Clinical Endocrinology & Metabolism) studied the relationship between intravenous kisspeptin-10 and LH pulse frequency in men. Jayasena et al. (2011, JCEM) examined sexually dimorphic patterns of reproductive-hormone measurement following kisspeptin-10 administration; that study also characterized the in vivo plasma half-life of intravenous kisspeptin-10, which is notably shorter than that of kisspeptin-54, consistent with its smaller size. An early human study by Dhillo et al. (2005, JCEM) examined kisspeptin-54 in relation to HPG axis signaling in males, providing the comparative pharmacology reference for KP-10 studies. ClinicalTrials.gov registry entries involving kisspeptin administration include NCT00914823, NCT02081924, and NCT05633966.