Dear Editor,
Neuronal pentraxin 2 (NPTX2; also known as NP2 or Narp) is an activity-regulated neuronal protein that plays a pivotal role in organizing excitatory synapses and maintaining functional network balance (1). Clinically, reduced NPTX2 levels, often reported in cerebrospinal fluid (CSF) and occasionally in peripheral blood, correlate closely with disrupted network synchrony and cognitive decline in neurodegenerative conditions, highlighting the potential of NPTX2 as a robust marker of synaptic integrity (2, 3, 4). However, its critical involvement extends beyond general cognition. NPTX2 profoundly influences motor control and learning through precise modulation of the excitation-inhibition (E-I) balance within corticomotor circuits. Specifically, it drives the postsynaptic clustering and stabilization of GluA1-containing AMPA receptors (AMPARs) selectively at synapses targeting fast-spiking, parvalbumin-positive (PV+) interneurons. This targeted clustering amplifies excitatory drive onto these interneurons, thereby enhancing perisomatic GABAergic feedforward inhibition of pyramidal neurons. This regulatory mechanism optimizes synaptic gain, sharpens action-potential timing, and enables spike-timing-dependent plasticity (STDP), which is critical for motor skill acquisition and fine sensorimotor processing (4, 5, 6).
In animal models, NPTX2 knockdown disrupts AMPAR trafficking to PV+ synapses, profoundly impairing cortical motor-map refinement and STDP and manifesting as significant deficits in motor adaptation and procedural learning (7, 8). Conversely, activity-induced NPTX2 upregulation restores proper AMPAR localization, normalizes primary motor cortex excitability, and strengthens feedforward inhibition. Electrophysiological assays confirm that this restoration improves the precision of sensorimotor transformations (9). Human data strongly corroborate these findings: low CSF NPTX2 levels in patients with Parkinson disease are significantly associated with bradykinesia and procedural memory impairments, whereas aerobic exercise interventions have been shown to acutely elevate NPTX2 and subsequently reinstate synaptic homeostasis (10, 11, 12). Mechanistically, NPTX2 orchestrates pentraxin signaling to regulate critical synaptic-scaling genes (eg, Arc and Homer), thereby facilitating AMPAR-dependent long-term potentiation (LTP), which is essential for motor-memory consolidation. Furthermore, by promoting PV+ interneuron synchronization, NPTX2 stabilizes the cortical gamma oscillations required for precise motor timing (13). Consequently, even modest shifts in NPTX2 expression can yield measurable effects on motor performance, positioning it as a key molecular anchor linking activity-dependent neuroplasticity to tangible behavioral motor outcomes.
Although general physical activity is widely recognized as a powerful driver of neurovascular support and baseline activity-dependent plasticity (14), its specific impact on NPTX2-mediated motor-learning pathways warrants closer scrutiny. It is plausible that not all forms of exercise engage this pathway equally. Novel paradigms that deeply engage sensorimotor circuits, such as skill-based motor practice, complex visuospatial motor training, or task-specific high-intensity interval training, are likely to be the most potent stimuli for upregulating or normalizing NPTX2 function and driving true motor learning rather than merely improving physiological fitness. To capitalize on this possibility, future empirical studies should combine targeted motor-learning tasks with preintervention and postintervention measures of NPTX2 via CSF or peripheral biomarkers. These studies should ideally be paired with advanced neurophysiological readouts, including transcranial magnetic stimulation (TMS) to assess motor cortex excitability and electroencephalography (EEG) or magnetoencephalography (MEG) to evaluate oscillatory network dynamics, as well as molecular analyses in corresponding animal models. Such translational, multimodal research will clarify causal links and optimize dose-response relationships involving modality, intensity, and volume, while also paving the way for tailored rehabilitation and neuroprotective strategies targeting synaptic resilience in motor-control disorders.
