The FRMPD4 gene (FERM and PDZ domain containing 4) encodes a multi-domain protein that is crucial for neuronal function, particularly involved in dendritic spine morphogenesis, synaptic transmission, and various signaling pathways. Here is a more detailed exploration based on your request:

### 1. Associated Genes:
While the summaries mention interaction with PSD-95, FRMPD4 is often associated with several other genes and proteins involved in synaptic function and signaling pathways, including:
- **SHANK proteins**: These are scaffold proteins that play critical roles in the structure and function of postsynaptic density.
- **GRIN1 (GluN1)**: A subunit of the NMDA receptor that mediates excitatory neurotransmission.
- **DLG4 (PSD-95)**: Involved in anchoring synaptic signaling proteins.
- **PTEN**: A phosphatase that regulates the signaling pathway involved in cell growth and survival.

### 2. Aging and Age-related Diseases:
Research related to FRMPD4 may reveal connections to aging through its role in maintaining synaptic integrity and function. Synaptic deficits are often observed in neurodegenerative diseases, which are associated with aging, such as:
- **Alzheimer's Disease**: Impairments in synaptic signaling and dendritic spine loss are common in Alzheimer's, and FRMPD4's regulatory functions may influence these pathways.
- **Huntington's Disease**: Synaptic dysfunctions have been linked to the pathogenesis of Huntington's, potentially implicating FRMPD4 in associated cellular processes.

However, more specialized studies would be needed to conclusively establish the relationship between FRMPD4 and these age-related conditions.

### 3. Drug Interactions:
Currently, specific drugs or drug classes targeting FRMPD4 have not been clearly defined in the available literature. However, compounds that affect excitatory neurotransmission or modulate signaling pathways involving phosphatidylinositol (such as phosphoinositide 3-kinase inhibitors) may indirectly influence FRMPD4 functions. Nonetheless, more research would be required to identify specific interactions or therapeutic drugs.

### 4. Pathways and Biological Processes:
The FRMPD4 gene is known to participate in a variety of cellular pathways and biological processes, including:
- **Dendritic Spine Development**: Essential for the formation and maturation of dendritic spines, which are critical for synaptic connectivity and plasticity.
- **Synaptic Transmission**: Involved in regulating the excitatory synaptic signaling critical for communication between neurons.
- **Phosphoinositide Signaling Pathway**: FRMPD4 binds to phosphatidylinositol 4,5-bisphosphate (PIP2), impacting various intracellular signaling cascades.

Overall, FRMPD4 plays a significant role in synaptic architecture and signaling, with potential implications for understanding neurological diseases, particularly those associated with aging. Further research is warranted to delineate these associations and explore its therapeutic potential.