The PMEPA1 gene (PMEPA1, Prostate Cancer-Associated Gene 1) has a multifaceted role in cellular signaling, especially concerning androgen and TGF-beta pathways. Below is an elaboration based on your queries:

### 1. Related Genes
PMEPA1 has associations with several other genes, particularly due to its role in the TGF-beta signaling pathway and androgen signaling. Some of these include:
- **SMAD2 and SMAD3**: Directly involved in TGF-beta signaling and interact with PMEPA1.
- **SMAD4**: Forms heteromeric complexes with phosphorylated SMAD2 and SMAD3, affected by PMEPA1 interactions.
- **NEDD4**: An E3 ubiquitin ligase that helps enhance AR degradation, regulated by PMEPA1.
- **AR (Androgen Receptor)**: Target of PMEPA1's negative regulatory functions.
- **ZFYVE9 (SARA)**: A protein involved in recruiting SMAD proteins to the TGF-beta receptor, potentially competed with by PMEPA1.

### 2. Aging and Age-Related Diseases
Although specific aging-related studies on PMEPA1 may be limited, its functions in cellular processes such as proliferation and apoptosis are critical in contexts like cancer and age-related diseases. Dysregulation of TGF-beta signaling has been implicated in many age-related conditions including:
- **Cancer**: As PMEPA1 may promote cancer cell proliferation through normalizing TGF-beta signaling and AR degradation.
- **Fibrosis**: TGF-beta is known to play a role in fibrosis, which can exacerbate age-related organ degeneration.
These pathways suggest that PMEPA1 could have roles in the aging process and the onset of age-related diseases, especially in cancer, where its overexpression could indicate poor prognosis.

### 3. Drug Interactions
While specific drugs targeting PMEPA1 directly might not be extensively documented, its involvement in the AR pathway does link it to compounds influencing androgen signaling. Examples include:
- **Androgen receptor antagonists** (e.g., Enzalutamide) used in prostate cancer treatment may indirectly interact with PMEPA1 pathway dynamics. 
- **TGF-beta inhibitors**: Drugs targeting TGF-beta signaling may also interact with PMEPA1 functionally, although specific agents would depend on the context of application.

### 4. Pathways and Biological Processes
PMEPA1 is involved in several key biological processes and pathways, including:
- **TGF-beta Signaling Pathway**: Negative regulation of signaling, affecting numerous downstream effects including cellular growth and differentiation.
- **Androgen Signaling Pathway**: Modulates the androgen receptor's signaling, influencing prostate cancer dynamics.
- **Ubiquitin-proteasome Pathway**: Involvement in the recruitment of NEDD4 leads to targeted degradation via ubiquitination.
- **Extracellular Matrix Production**: By acting on TGF-beta signaling, PMEPA1 may influence the production of extracellular matrix components, which is vital in tissue remodeling and fibrosis.

Together, these interactions position PMEPA1 as a significant player in both normal physiology and pathophysiology related to aging and diseases like cancer. Its role as a regulatory node in critical signaling pathways highlights its potential importance in therapeutic contexts.