Lecticans

Lecticans are a family of extracellular matrix proteoglycans found in vertebrate nervous systems, particularly the brain. The four best-known members are aggrecan, brevican, neurocan, and versican. Collectively, they are classified as chondroitin sulfate proteoglycans (CSPGs) with hyaluronan-binding capacity, and they play a central role in organizing the neural extracellular matrix and peri-neuronal nets.

Structurally, lecticans consist of a core protein that carries covalently attached glycosaminoglycan (GAG) chains and a hyaluronan-binding region at the N-terminus, enabling attachment to the extracellular matrix. The C-terminal region contains a G3 domain that may contribute to interactions with other matrix components. The combination of proteoglycan core and CS chains gives lecticans the ability to modulate cell adhesion, migration, and synaptic connectivity.

Biologically, lecticans regulate neural development by influencing neuronal migration, axon guidance, and synapse formation. In the mature central nervous system, perineuronal nets formed in part by lecticans help stabilize established neural circuits and limit further plasticity. Experimental manipulation of lectican levels or integrity can alter plasticity, with enzymatic digestion often enhancing or reopening critical periods of learning in animal models.

Expression and distribution vary by lectican family member and developmental stage. Neurocan and brevican are prominent during early development, while versican and aggrecan show distinct regional patterns; aggrecan is more abundant in cartilage but is also present in CNS tissues to a lesser extent. Lecticans are also expressed in the retina and other parts of the CNS.

Proteolytic processing by enzymes such as matrix metalloproteinases and ADAMTS modulates their structure and function, generating fragments that can have separate biological effects. In research and medicine, lecticans are studied for their roles in development, injury response, and neural regeneration, as well as for strategies to modulate CNS plasticity.