RC3

RC3, also known as neurogranin, is a neuron-specific calmodulin-binding protein that functions as a regulator of calmodulin signaling. It is encoded by the RGN gene in humans and is highly expressed in forebrain regions such as the hippocampus and cerebral cortex. RC3 was originally identified in rat brain tissue and named RC3 for its regulatory role in calmodulin signaling.

In terms of structure, RC3 is a small cytosolic protein containing calmodulin-binding domains that interact with apo-calmodulin. In resting conditions when intracellular Ca2+ is low, RC3 binds calmodulin, limiting its availability. Upon calcium influx, calmodulin dissociates from RC3, increasing the pool of free calmodulin to participate in calcium-dependent signaling pathways that influence synaptic activity.

Physiological role: RC3 is implicated in synaptic plasticity processes such as long-term potentiation, learning, and memory. Disruption of RC3 expression or function has been studied in the context of neurodegenerative diseases; for instance, neurogranin levels in cerebrospinal fluid have been explored as biomarkers for synaptic dysfunction and Alzheimer's disease progression. However, the exact contribution of RC3 to disease pathology remains under investigation.