### Gene Overview
**Gene Symbol:** PPP1R3D  
**Function:** The PPP1R3D gene encodes a regulatory protein that targets protein phosphatase 1 (PP1) to glycogen granules. This action is vital for the regulation of glycogen metabolism and various cellular processes, including muscle contractility and protein synthesis.

### 1. Associated Genes
PPP1R3D is particularly associated with the following genes:
- **PPP1CA:** Encodes one of the catalytic subunits of protein phosphatase 1, which directly interacts with PPP1R3D.
- **GSK3B (Glycogen synthase kinase 3 beta):** Involved in glycogen metabolism and is regulated by phosphorylation events mediated by PP1.
- **PRKAA2 (AMP-activated protein kinase):** Important in energy homeostasis; also interacts in signaling pathways that modulate glycogen metabolism.
- **PYGL (Glycogen phosphorylase, liver):** Enzyme that plays a key role in glycogen breakdown, linking it with the glycogen-targeting function of PPP1R3D.

### 2. Aging and Age-Related Diseases
While specific studies directly associating PPP1R3D with aging or age-related diseases are limited, its role in glycogen metabolism suggests potential implications in:
- **Type 2 Diabetes:** Since proper glycogen metabolism is crucial for glucose homeostasis, dysregulation of PPP1R3D may contribute to insulin resistance and metabolic disorders commonly associated with aging.
- **Neurological Diseases:** Given the involvement of phosphorylation in memory and learning, alterations in PP1 activity, potentially influenced by PPP1R3D, could affect cognitive decline in aging.
- **Cardiovascular Disease:** Aging can affect muscle contractility, and dysfunction in regulatory pathways involving PPP1R3D might contribute to age-related cardiac issues.

### 3. Drug and Drug Classes Interactions
There is no explicit information regarding specific drugs that directly target PPP1R3D; however, drugs that influence glycogen metabolism can indirectly affect this gene's activity. Examples include:
- **Metformin:** Used in Type 2 diabetes management, it affects glucose metabolism and may influence pathways involving PP1 and its regulators.
- **SGLT2 Inhibitors:** These also impact glucose homeostasis and may have downstream effects on glycogen metabolism regulated by PPP1R3D.

### 4. Pathways and Biological Processes
PPP1R3D is involved in several significant biological pathways and processes:
- **Glycogen Metabolism:** The primary role of PPP1R3D is in the modulation of glycogen levels through interaction with PP1.
- **Regulation of Muscle Contraction:** Through its influence on glycogen metabolism in muscle tissues, PPP1R3D plays a role in muscle contraction.
- **Cell Cycle Regulation:** Since PP1 is involved in various phases of the cell cycle, PPP1R3D plays an indirect role in regulating cell division.
- **Protein Phosphorylation:** Contributes to the regulation of protein phosphorylation status, influencing signaling pathways critically involved in cellular responses.

### Conclusion
PPP1R3D is a critical component in glycogen metabolism and the broader regulation of cellular processes through its association with PP1. Its genetic interactions, potential implications in age-related diseases, and involvement in fundamental biological pathways emphasize its significance in both health and disease.