### 1. Associated Genes
In addition to the mentioned interactions with insulin receptor (INSR), insulin-like growth factor 1 receptor (IGF1R), and fibroblast growth factor receptor 1 (FGFR1), IRS4 has been associated with several other genes involved in cellular signaling and metabolism, including:

- **IRS1** and **IRS2**: Other insulin receptor substrates that may have competitive or regulatory interactions with IRS4.
- **AKT1**: Also known as protein kinase B (PKB), a central player in the signaling pathways mediating metabolic and growth factor responses.
- **GRB2**: Growth factor receptor-bound protein 2, which enhances signaling pathways.
- **EPHB2**: A receptor that may be associated with IRS4 in hepatoblastoma signaling and development.
- **MAPK1**: Mitogen-activated protein kinase 1, which is part of the signaling cascade enhanced by the interaction with IRS4.

### 2. Aging and Age-Related Diseases
IRS4 has been implicated in the regulation of glucose homeostasis and, by extension, age-related conditions such as Type 2 Diabetes Mellitus (T2DM) and obesity, which are commonly seen in aging populations. Alterations in insulin signaling pathways, including those involving IRS4, are thought to contribute to increased insulin resistance and metabolic dysregulation with age. Its role in cell proliferation and differentiation may also tie IRS4 activity to age-related cancers and tissue degeneration processes.

### 3. Drug Interactions
While the direct interaction of specific drugs with IRS4 is not extensively characterized, the gene is involved in pathways related to insulin signaling, which can be influenced by:

- **Insulin Therapies**: Such as exogenous insulin and insulin sensitizers (e.g., Metformin) that modulate the effects of insulin signaling.
- **Growth Hormone (GH)** signaling agents: Some GH analogs or treatments might potentially influence pathways involving IRS4.
- **Tyrosine Kinase Inhibitors**: These can affect downstream signaling pathways involving IRS4, particularly in cancer therapeutics that target growth factor signaling.

### 4. Pathways and Biological Processes
IRS4 is involved in several critical biological pathways including:

- **Insulin Signaling Pathway**: Mediates the cellular effects of insulin, influencing glucose uptake, metabolism, and storage.
- **IGF Signaling Pathway**: Participates in cellular growth and development responses to insulin-like growth factor, playing a role in mitogenesis and cell survival.
- **MAPK Signaling Pathway**: Contributes to the activation of the MAPK cascade, which is crucial for cell proliferation and differentiation.
- **Cytokine Signaling Pathway**: May play a role in the signaling mechanism of various cytokines, contributing to immune responses and inflammation.
- **Cell Proliferation and Differentiation**: Particularly relevant in the context of liver development and cancers such as hepatoblastoma.

Overall, the IRS4 gene serves as a critical mediator in various signaling cascades that not only affect metabolic regulation but also contribute to developmental processes and potentially to the pathogenesis of age-related diseases.