### PSMB3 Gene Summary
**Gene Symbol:** PSMB3  
**Function:** The PSMB3 gene encodes a beta subunit of the 20S proteasome core, part of a multicatalytic proteinase complex involved in degrading ubiquitinated proteins, thus playing a crucial role in protein homeostasis, cell cycle regulation, and responses to oxidative stress.

### 1. Associated Genes
PSMB3 has functional associations with several other genes within the proteasome and ubiquitin-proteasome system, including:
- **PSMA1 to PSMA7 (Alpha subunits):** These genes encode the alpha subunits of the proteasome.
- **PSMB1, PSMB2, PSMB4, PSMB5, and PSMB6:** Other beta subunits that are part of the core proteasome complex.
- **Ubiquitin (UB):** Ubiquitin protein is critical for tagging proteins for degradation via the proteasome.
- **VCP (Valosin-containing protein):** Involved in the recognition of ubiquitinated substrates.
- **RPN1 to RPN5:** Regulatory particles that associate with the 26S proteasome.

### 2. Aging and Age-Related Diseases
- **Protein Homeostasis and Aging:** The proteasome system, including PSMB3, is critical for maintaining protein homeostasis, which is essential for cellular function. Impaired proteasomal activity has been linked to aging, leading to the accumulation of damaged proteins and contributing to age-related cellular decline.
- **Neurodegenerative Diseases:** There is a known correlation between defective proteasome function and neurodegenerative diseases like Alzheimer’s and Parkinson’s. Abnormal protein aggregates, such as amyloid-beta, are often cleared by the proteasome, and age-related decreases in proteasome efficiency can exacerbate these conditions.

### 3. Drug Interactions
- **Proteasome Inhibitors:** Certain drugs that target the proteasome, such as:
  - **Bortezomib:** Used primarily in the treatment of multiple myeloma and certain types of lymphoma. It selectively inhibits the proteasome.
  - **Carfilzomib:** Another proteasome inhibitor used in multiple myeloma therapy.
  - **Ixazomib:** An oral proteasome inhibitor for the treatment of multiple myeloma.
- **Anti-inflammatory Drugs:** Some anti-inflammatory drugs may indirectly affect proteasomal activity, thus modulating the pathways in which PSMB3 is involved.

### 4. Biological Pathways and Processes
**Key Pathways:**
- **Ubiquitin-mediated proteolysis:** The PSMB3 gene plays a central role in the ubiquitin-proteasome pathway, essential for protein turnover and regulation.
- **Antigen Presentation:** The immunoproteasome, which includes PSMB3, plays a crucial part in processing peptides for presentation on MHC class I molecules in immune responses.
- **Cell Cycle Regulation:** By degrading cyclins and other regulatory proteins, PSMB3 contributes to the control of the cell cycle.

**Biological Processes:**
- **Protein Catabolism:** Involvement in the breakdown of cellular proteins via proteolysis.
- **Regulation of Apoptosis:** It participates in the regulation of apoptosis by degrading anti-apoptotic proteins.
- **Response to Oxidative Stress:** The proteasome system, including PSMB3, is involved in mitigating cellular damage from reactive oxygen species (ROS).
- **Spermatogenesis:** PSMB3 may contribute to ubiquitin-independent proteolytic pathways in testes.

Overall, PSMB3 is a critical component of the proteasome that connects various cellular functions and pathways, influencing not only normal physiology but also the pathogenesis of diseases associated with aging and cellular stress.