HMMR
Description
The HMMR (hyaluronan mediated motility receptor) is a protein-coding gene located on chromosome 5.
Hyaluronan-mediated motility receptor (HMMR), also known as RHAMM (Receptor for Hyaluronan Mediated Motility) or CD168, is a protein encoded by the HMMR gene in humans. HMMR was initially identified as a soluble protein that influences cell migration and binds to hyaluronan. Unlike CD44, the primary hyaluronan (HA) receptor, HMMR lacks a membrane-spanning domain and signal sequence for secretion. HMMR is localized within the cell and is unconventionally transported to the cell surface in response to stimuli such as wounding and cytokines like TGF-β. The specific mechanism for HMMR's extracellular transport is unclear but may involve transport channels, proteins, flippase activity, or exocytosis. Inside the cell, HMMR interacts with microtubules and, alongside BRCA1 and BARD1, participates in regulating mitosis and maintaining mitotic spindle integrity. HMMR also directly binds to ERK1 and forms complexes with ERK1,2 and MEK1, suggesting a role as a scaffolding protein that targets these MAP kinases to the nucleus. In the extracellular space, HMMR interacts with CD44 and, upon binding to hyaluronan, activates intracellular signaling pathways, primarily the MAPK pathway through ERK1,2 activation. Alternative splicing gives rise to variations of HMMR, and alternative start codon usage has been proposed in mice and directly observed in humans.
HMMR is also known as CD168, IHABP, RHAMM.
