### DLG4 Gene Overview

**Gene Symbol**: DLG4  
**Gene Name**: Discs Large Homolog 4

### 1. Associated Genes
In addition to DLG2, which has been mentioned, DLG4 interacts with several other genes and proteins, such as:

- **GRIN2A, GRIN2B**: Encoding NMDA receptor subunits that DLG4 interacts with, facilitating the clustering of NMDA receptors.
- **GRIA1, GRIA2**: Encoding subunits of AMPA receptors, also involved in synaptic transmission.
- **SHANK proteins (e.g., SHANK1, SHANK2)**: Known to interact with DLG4 and play a role in organizing postsynaptic density.
- **PSD-95**: Another member of the MAGUK family that works in conjunction with DLG4 in synaptic signaling and clustering.

### 2. Aging and Age-Related Diseases
DLG4 has been implicated in various neurodegenerative conditions and cognitive decline associated with aging, including:

- **Alzheimer's Disease**: Alterations in synaptic function and plasticity due to DLG4 dysregulation may contribute to the synaptic failure observed in Alzheimer's pathology.
- **Schizophrenia**: Genetic variations in DLG4 have been associated with schizophrenia, which includes cognitive deficits often exacerbated by age.
- **Autism Spectrum Disorder (ASD)**: Mutations in DLG4 have been implicated in ASD, correlating with synaptic dysfunctions that may manifest or progress in severity with age.

### 3. Drug Interactions
Research has identified interactions of DLG4 with several drug classes that target synaptic function:

- **NMDA Receptor Antagonists**: Such as ketamine, which can impact DLG4 signaling pathways by modulating NMDA receptor activity.
- **Cyclic GMP Phosphodiesterase Inhibitors**: These drugs could indirectly influence DLG4 functions through modulation of signaling pathways related to synaptic plasticity.
- **Antiepileptics**: Some studies suggest that certain antiepileptic drugs may interact with DLG4-mediated pathways and affect synaptic transmission.

### 4. Pathways and Biological Processes
DLG4 is involved in several crucial biological pathways and processes:

- **Synaptic Signaling Pathway**: DLG4 plays an essential role in the synaptic signaling pathway, including the clustering and stabilization of receptors at the postsynaptic density.
- **Postsynaptic Density Formation**: DLG4 components facilitate the structural formation of postsynaptic density, essential for synaptic strength and plasticity.
- **Ion Channel Regulation**: Involved in the regulation and clustering of ion channels, particularly NMDA and AMPA receptors.
- **Regulation of Synaptic Plasticity**: DLG4 is critical for both long-term potentiation (LTP) and long-term depression (LTD), two key mechanisms underlying learning and memory.
- **Intracellular Trafficking**: Regulates the trafficking of synaptic proteins, which impacts synaptic transmission and homeostasis.

Through these functions, DLG4 plays a vital role in maintaining synaptic integrity, plasticity, and overall neural communication, significantly influencing cognitive functions and related disorders throughout the lifespan.