### PSMB4 Gene Overview

**Gene Symbol**: PSMB4  
**Location**: Human chromosome 17

The PSMB4 gene encodes a beta subunit of the 20S proteasome complex, which plays a critical role in protein degradation. It is a member of the proteasome B-type family and is involved in both the standard proteolytic pathway as well as the immunoproteasome function that provides peptides for MHC class I presentation.

### 1. Associated Genes

While the summaries from NCBI and UniProt provided limited information about specific gene interactions, PSMB4 is known to interact with several other genes/proteins, including:

- **PSMB5**: Also a beta subunit of the proteasome, forming part of the same complex.
- **PSMB6**: Another proteasome beta subunit implicated in protein degradation.
- **PSMA2, PSMA3**: These are alpha subunits that together with PSMB4 form the 20S proteasome.
- **UBC**: Ubiquitin conjugates that are essential for targeting proteins to be degraded by the proteasome.

Additional studies often reveal functional partnerships with molecular chaperones and degradation-associated proteins, but precise associations can vary based on research focus.

### 2. Aging and Age-Related Diseases

Research has implicated PSMB4 in several age-related phenomena:

- **Protein Homeostasis**: The proteasome is heavily involved in the maintenance of protein quality control. With aging, the efficiency of the proteasome may decline, contributing to the accumulation of damaged proteins, which is linked to various age-related diseases such as neurodegenerative disorders (e.g., Alzheimer's disease).

- **Neurodegenerative Diseases**: Dysregulation of proteasome activity, including that mediated by PSMB4, has been linked to the pathology of diseases like Parkinson's, suggesting that this gene may have an indirect role in the progression of these disorders.

- **Immune Function**: Age-related decline in immune function ("immunosenescence") has been associated with changes in proteasome function, affecting the antigen presentation necessary for mounting immune responses.

### 3. Known Drugs or Drug Classes

While there are no direct "drugs" that target PSMB4 specifically, it is associated with various drug classes that influence proteasome activity:

- **Proteasome Inhibitors**: 
  - **Bortezomib**: Used in multiple myeloma and some types of lymphoma; it inhibits the proteasome, altering the degradation of pro-apoptotic factors.
  - **Carfilzomib**: Another proteasome inhibitor, like bortezomib, used in the treatment of hematological cancers.

Proteasome inhibitors are of particular interest in cancer therapy due to their role in inducing apoptosis in cancer cells by affecting the balance of pro- and anti-apoptotic proteins.

### 4. Pathways and Biological Processes

PSMB4 is involved in several critical pathways and biological processes, including:

- **Proteolytic Process**: Central to the proteasome's functionality, involved in the degradation of ubiquitinated proteins.
- **Antigen Processing & Presentation**: The immunoproteasome mediates the generation of peptides for MHC class I molecules.
- **Regulation of Cellular Functions**: By degrading misfolded proteins and those no longer needed, PSMB4 plays a role in maintaining cellular protein homeostasis.
- **Cell Cycle Regulation**: The proteasome pathway contributes to the regulation of the cell cycle by controlling the degradation of key regulatory proteins.

### Conclusion

The PSMB4 gene is integral to the proteasome's function in maintaining protein quality and cellular homeostasis. Its role becomes increasingly relevant in the context of aging and age-related diseases, where aberrations in protein degradation can lead to pathological manifestations. Ongoing research into PSMB4 could yield insights into targeted therapies for aging and cancer-related conditions.