The ACTR3B gene, also known as Actin-Related Protein 3B, is a member of the actin-related protein (ARP) family and plays an important role in cytoskeletal organization, particularly in the regulation of actin polymerization. Below is a detailed exploration of your queries regarding ACTR3B:

### 1. Associated Genes:
While the NCBI and UniProt summaries did not specify additional genes associated with ACTR3B, studies indicate that it may interact with several other proteins involved in actin dynamics, including:
- **ACTR3**: Another member of the ARP family that works in the same complexes.
- **ARPC1A** and **ARPC4**: Components of the Arp2/3 complex that cooperate with ACTR3B.
- **Nucleation-Promoting Factors (NPFs)** like **WAVE** and **Scar** that can activate the Arp2/3 complex for actin branching.
- Other genes implicated in cancer metastasis and cytoskeletal dynamics could also show functional interactions, but these would require specific research context to outline clearly.

### 2. Aging and Age-Related Diseases:
Research into the role of ACTR3B in aging and age-related diseases suggests some potential involvement:
- **Cell Motility**: Changes in actin dynamics have been linked to cellular senescence and impaired wound healing, which can be exacerbated with age.
- **Cancer Metastasis**: Since ACTR3B has been suggested to decrease the metastatic potential of tumors, alterations in its function might relate to the increased cancer incidence seen with aging.
- **Neurodegenerative Diseases**: Dysregulation of actin cytoskeleton dynamics is often implicated in diseases such as Alzheimer's, where improper cytoskeletal regulation may contribute to tau pathology.

### 3. Drug or Drug Classes:
While ACTR3B is not directly targeted by specific medications, several drug classes may influence pathways related to actin dynamics:
- **Cytoskeletal Disruptors**: Drugs like cytochalasins and latrunculin target actin polymerization, which could indirectly affect ACTR3B function as part of the Arp2/3 complex.
- **Chemotherapeutics**: Certain chemotherapeutic agents may interact with cellular motility and cytoskeletal organization, which could affect expression levels or functional outcomes linked to ACTR3B.

### 4. Pathways and Biological Processes:
The ACTR3B gene is involved in several key biological processes and pathways:
- **Actin Nucleation and Polymerization**: As a component of the Arp2/3 complex, ACTR3B is vital for the nucleation of new actin filaments, particularly in the formation of branched actin networks.
- **Cell Migration and Motility**: It plays a critical role in processes such as cell migration, which is essential during development, wound healing, and immune responses.
- **Endocytosis and Membrane Trafficking**: ACTR3B is also implicated in cellular mechanisms involving endocytosis, where actin dynamics contribute to membrane invagination and vesicle formation.
- **Signal Transduction**: Through its interactions with various proteins, ACTR3B may also be involved in signaling pathways that regulate various cellular functions, including proliferation and apoptosis.

Overall, the ACTR3B gene is foundational to understanding cytoskeletal regulation, cellular dynamics, and implications in various biological processes and diseases, particularly related to cancer EMT (epithelial-mesenchymal transition) and possibly neurodegenerative conditions. Research on this gene continues to expand our understanding of its roles in health and disease.