### Overview of WDR91 Gene

**Gene Symbol:** WDR91  
**Location:** Cytosol; early endosome membrane; late endosome membrane  
**Function:** WDR91 functions as a negative regulator of the phosphatidylinositol 3-kinase (PI3K) signaling pathway, particularly in the context of endosomal membranes. It influences various cellular processes including the transport of materials from early to late endosomes and the degradation of cellular components via lysosomal activity.

### Associated Genes
While the summaries provided focus on WDR91's interactions primarily with **BECN1**, there are additional gene interactions typically associated with WDR91 based on its roles in endosomal transport and PI3K regulation:
- **PIK3C3** (Phosphatidylinositol 3-kinase catalytic subunit type 3): Involved in the class III PI3K pathway.
- **RAB proteins** (like RAB5, RAB7): These are involved in endosomal trafficking.
- **VPS34**: Associated with class III PI3K activity and may share functional roles with WDR91.
- **BST2 (Tetherin)**: As mentioned, WDR91 indirectly facilitates its delivery to late endosomes.

### Aging and Age-Related Diseases
While specific research directly linking WDR91 to aging or age-related diseases may be limited, its role in cellular signaling and proteostasis could imply relevance to:
- **Neurodegenerative Diseases**: Dysregulation of PI3K signaling and endosomal pathways has been linked to conditions such as Alzheimer’s disease and Parkinson’s disease. 
- **Cancer**: Alterations in endosomal trafficking and PI3K signaling pathways are critical in oncogenesis and tumor suppression, suggesting potential implications for age-related tumorigenesis.

### Drug Interactions
There are currently no specific drugs or drug classes directly known to interact with WDR91. However, given its role in PI3K signaling, inhibitors or modulators of the PI3K pathway (like **PI3K inhibitors**, **mTOR inhibitors**, or **copanlisib**) could potentially influence WDR91 indirectly through pathway modulation.

### Pathways and Biological Processes
WDR91 is involved in several important biological processes, including:
- **Endosomal Transport**: Facilitating the transport of cargo from early to late endosomes.
- **Regulation of PI3K Activity**: Modulating signaling pathways that are essential for various cellular responses including survival, growth, and metabolism.
- **Phagosome Maturation**: Involvement in the maturation process of phagosomes contributing to immune responses.
- **Cellular Protein Catabolic Process**: Participating in the regulation of protein degradation pathways that help maintain cellular homeostasis.
- **Meiosis**: Functioningally inferred roles during the meiotic processes, suggesting its potential implications in reproductive biology.

### Conclusion
The WDR91 gene plays a crucial role in the regulation of key intracellular processes related to endosomal trafficking and PI3K activity. Its connections to aging and age-related diseases, while not exhaustive, indicate a need for further exploration of its functions in various biological contexts. The understanding of WDR91's interactions, especially with other genes and pathways, is essential in comprehending its full physiological roles and potential implications in health and disease.