coreceptoren

Coreceptoren, or co-receptors, are cell-surface proteins that work together with primary receptors to bind ligands or to transduce signals. They are not usually sufficient on their own to elicit full cellular responses but modulate affinity, specificity, and downstream signaling by forming receptor complexes or recruiting signaling molecules. Co-receptors can influence endocytosis and trafficking of ligands.

In virology, co-receptors facilitate entry of certain viruses. For example HIV requires the primary receptor CD4 and the coreceptors CCR5 or CXCR4 to fuse with the cell membrane. Genetic variants reducing CCR5 expression can confer resistance to infection with specific HIV strains.

In immune signaling, co-receptors lower the activation threshold. The B cell co-receptor complex consisting of CD19, CD21 (CR2) and CD81 enhances B cell receptor signaling in response to antigen. Other co-receptors complement T cell receptor signaling, such as CD28 providing co-stimulatory signals that support activation and proliferation.

In development and neuroscience, coreceptors such as integrins, neuropilins, or other proteoglycans participate in growth factor or guidance cue signaling by forming complexes with primary receptors, influencing processes like axon guidance and angiogenesis.

Clinical relevance: Co-receptors are targets for therapies and vaccines. Blocking co-receptor interactions can prevent viral entry or dampen pathological signaling. Genetic variation in co-receptor expression can affect susceptibility to diseases.