The GRK4 gene (G protein-coupled receptor kinase 4) is an important player in the regulation of G protein-coupled receptors (GPCRs) through its kinase activity. Here is additional information related to your queries:

### 1. Associated Genes
GRK4 may interact with or be associated with other genes involved in GPCR signaling and associated pathways, including but not limited to:
- **GRK3**: Another member of the GRK family, also involved in GPCR phosphorylation.
- **AR**: Androgen Receptor, as GRK4 can influence the signaling pathways related to steroid receptors.
- **DRD3**: Dopamine receptor D3, which is directly phosphorylated by GRK4 isoforms.
- **ADRB2**: Adrenergic receptor B2, another direct target for phosphorylation by GRK4.
- **ACTB**: While not directly associated with GRK4 function, changes in actin dynamics can affect GPCR signaling and may relate to GRK4 activity.

### 2. Aging and Age-Related Diseases
There is some evidence linking GRK4 to hypertension, which itself can be influenced by aging. Additionally, changes in GPCR signaling due to modifications in GRK expression and activity have been implicated in various age-related conditions, including:
- **Hypertension**: GRK4 variants (particularly those that are associated with increased kinase activity) can lead to heightened desensitization of adrenergic receptors, contributing to the development of hypertension in older adults.
- **Cardiovascular Diseases**: Given the role of GPCRs in cardiovascular function, dysregulation of GRK4 has been implicated in heart diseases, which often correlate with aging.

### 3. Drug Interactions
While specific drugs targeting GRK4 may not be well-established, GRK4 is involved in the signaling pathways of various receptors that can be modulated pharmacologically. Classes of drugs that may impact GRK4-related pathways include:
- **Beta-blockers**: These target adrenergic receptors, and GRK4 plays a role in their regulatory dynamics.
- **Calcium channel blockers**: Certain GPCRs regulated by GRK4 can influence calcium signaling pathways in vascular smooth muscle.
- **Antihypertensives**: Medications that affect GPCR signaling pathways, potentially influencing GRK4 activity indirectly.

### 4. Pathways and Biological Processes
GRK4 is involved in several critical biological pathways and processes, such as:
- **G protein-coupled receptor signaling pathway**: Phosphorylating activated GPCRs leads to receptor desensitization.
- **Regulation of signaling cascades**: By modulating the activity of various GPCRs, GRK4 influences pathways like those initiated by adrenaline, dopamine, and angiotensin.
- **Phosphorylation**: As a Ser/Thr kinase, it plays a role in post-translational modifications essential for regulating protein interactions and functions.

In summary, GRK4's involvement in GPCR desensitization ties it to a range of physiological processes, drug interactions, and potential implications in aging and disease states. This positions GRK4 as an important target for understanding the pharmacodynamics of drugs acting on GPCRs and their role in the pathophysiology of disorders like hypertension.