### PSMD5 Gene Overview

**Gene Symbol:** PSMD5  
**Function:** The PSMD5 gene encodes a non-ATPase subunit of the 19S regulatory complex of the 26S proteasome. This gene plays a crucial role in proteasome assembly, functioning as a chaperone during the assembly of the regulatory base subcomplex.

### 1. Associated Genes
PSMD5 interacts with several other genes that encode subunits of the proteasome or related protein complexes. Some of these include:

- **PSMC1** (Proteasome 26S subunit, ATPase 1)
- **PSMC2** (Proteasome 26S subunit, ATPase 2)
- **PSMD2** (Proteasome 26S subunit, non-ATPase 2)
- **PSMD10** (Proteasome 26S subunit, non-ATPase 10)
- **PSMC4** (Proteasome 26S subunit, ATPase 4)
- **PSMC5** (Proteasome 26S subunit, ATPase 5)
- **PAAF1** (Proteasome assembly antibody factor 1)  

These genes are involved in the composition and function of the proteasome complex.

### 2. Aging and Age-Related Diseases
There is emerging evidence linking proteasomal function, including components like PSMD5, to aging and age-related diseases. Key points include:

- **Protein Homeostasis:** The proteasome plays a crucial role in maintaining protein homeostasis by degrading misfolded or damaged proteins. As organisms age, the efficiency of the proteasome can decline, leading to the accumulation of damaged proteins and cellular stress.
- **Neurodegeneration:** Dysregulation of the proteasome has been implicated in neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's disease, where clearance of toxic protein aggregates becomes compromised.
- **Cellular Senescence:** The function of PSMD5 may influence cellular senescence, a state associated with aging and age-related dysfunction, partly through modulation of the expression and degradation of cell cycle regulators.

### 3. Drugs and Drug Classes
While there aren't specific drugs that target PSMD5 directly, the activity of proteasome inhibitors, such as:

- **Bortezomib:** A proteasome inhibitor used in the treatment of multiple myeloma and some types of lymphoma.
- **Carfilzomib and Ixazomib:** Other proteasome inhibitors in clinical use for hematological malignancies.

These drugs indirectly affect the functions of PSMD5 by inhibiting the overall proteasome activity, impacting the degradation pathways in which PSMD5 participates.

### 4. Pathways and Biological Processes
PSMD5 is involved in several biological processes, including:

- **Proteasome-mediated proteolysis:** The core function of PSMD5 is integrated into the proteasomal degradation pathway, crucial for regulating various cellular processes by controlling protein levels.
- **Cell cycle regulation:** By influencing the degradation of cyclins and other regulators, PSMD5 contributes to appropriate cell cycle progression.
- **Response to oxidative stress:** The proteasome, with help from PSMD5, is involved in managing oxidative stress by degrading damaged proteins.
- **Antigen processing and presentation:** In the context of immune response, proteasomal degradation is key for presenting peptides on MHC Class I molecules.

Understanding the role of PSMD5 provides insights into both basic cellular functions as well as pathological states, highlighting its significance in research related to aging, cancer, and neurodegenerative diseases.