The SPPL2C gene encodes a membrane-associated aspartic protease that primarily functions in spermatogenesis and cellular signaling through the processing of specific proteins. Below, I have provided additional details relevant to your queries, with research data available up to October 2023:

### 1. Associated Genes:
SPPL2C has been studied in relation to various genes involved in spermatogenesis and intracellular signaling. While specific gene interactions may not be exhaustively characterized, potential associated genes include:

- **PLN (Phospholamban)**: Involved in calcium homeostasis within cardiac muscle cells and may have relevance in spermatogenesis biology.
- **SNARE proteins** (e.g., **SNAP23, VAMP7**): These proteins are integral to vesicular trafficking and exocytosis and are processed by SPPL2C.
- **PIK3CA**: Potential involvement in signaling pathways that regulate cell growth and metabolism, which may intersect with SPPL2C's function in spermatogenesis.

### 2. Aging or Age-Related Diseases:
While specific studies directly linking SPPL2C to aging or age-related diseases may be limited, general insights can be mentioned:

- **Aging and Fertility Decline**: SPPL2C's role in spermatogenesis implies that it could be involved in age-related fertility decline in males. As the efficiency of spermatogenesis decreases with age, the ability of SPPL2C to process tail-anchored and SNARE proteins could be affected.
- **Age-Related Cellular Changes**: The role of SPPL2C in calcium homeostasis might influence aging-related cellular processes since dysregulation of calcium signaling is associated with various age-related conditions, including neurodegenerative diseases and metabolic disorders.

### 3. Drug Interactions:
Currently, there are no well-established drugs or drug classes specifically known to target SPPL2C. However, as a protease, it is conceivable that protease inhibitors or pathways modulating calcium homeostasis could indirectly affect its function.

Despite limited information, potential interactions with drugs targeting:

- **Calcium channels**: Given SPPL2C's role in modulating intracellular Ca²⁺ levels, calcium channel blockers might indirectly influence its activities.
- **Protease inhibitors**: Targeting the broader class of intramembrane-cleaving aspartic proteases could share novel therapeutic implications in the context of SPPL2C.

### 4. Pathways and Biological Processes:
SPPL2C is involved in several biological processes and pathways including:

- **Spermatogenesis**: Directly involved in the maturation of sperm cells through proteolytic processing of SNARE proteins which modulate vesicular trafficking and compartmentalization in spermatids.
- **Calcium Ion Homeostasis**: By cleaving proteins that regulate calcium levels, this gene plays a role in maintaining proper calcium signaling within cells.
- **Membrane Protein Proteolysis**: It has a key role in the proteolysis of tail-anchored membrane proteins, influencing their function and turnover at the endoplasmic reticulum membrane.

In summary, SPPL2C's activity as a sperm-specific intramembrane-cleaving protease highlights its crucial role in spermatogenesis and potential implications in aging and reproductive health. Current knowledge regarding its interactions, disease associations, and drug interactions remains an area for further research.