RANKL

RANKL (also known as TNF-related activation-induced cytokine), or receptor activator of nuclear factor-κB ligand, was first discovered as a key player in the RANKL/RANK/OPG osteoclast formation pathway.

Osteoprotegerin (OPG) is a secretory glycoprotein that is a family member of the TNF receptor (TNFR) superfamily. Osteoprotegerin protects bone by blocking osteoclastogenesis and increasing bone density. Unlike other TNFRs, osteoprotegerin lacks a transmembrane domain as well as any apparent cell-associated signals. High levels of osteoprotegerin mRNA are found in specialized tissues such as lung, heart, kidney, and placenta. There is evidence that osteoprotegerin plays a role in degenerative arterial disease.

Apoptosis, or programmed cell death, is a normal component of cellular differentiation and the development of multicellular organisms. Receptor activator of NF-kB (RANK) lacks significant homology with the other family members of the tumor necrosis factor receptor (TNFR) superfamily. The cytoplasmic domain of RANK interacts with the tumor necrosis factor receptor associated factors, adaptor proteins such as TRAF2, TRAF5 and TRAF6.

RANKL is the ligand for the receptor activator of NFkB (RANK) that belongs to the tumor necrosis factor receptor (TNFR) superfamily. RANK overexpression induces the NFkB and c-Jun-terminal kinase (JNK) downstream pathways. This pathway has been studied in detail in the bone remodeling system with regards to osteoclast activity and induction.

Extracellular Signal-Regulated Kinases (ERK) also known as the Mitogen-activated Protein Kinase (MAPK), MAPK/ERK proteins are a family of protein-serine/threonine kinases that are activated via the phosphorylation of tyrosine. MAPK/ERK are activated by diverse mechanisms.