### SEMA4D Gene Overview

**Gene Symbol**: SEMA4D  
**Location**: Chromosome 3 (3p14.3)  
**Description**: The SEMA4D gene encodes a member of the semaphorin family, which is involved in various signaling processes, including neuronal guidance and immune response. It functions primarily as a cell surface receptor that influences several downstream signaling pathways.

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### 1. Associated Genes
In addition to its roles in signaling pathways involving PLXNB1 and PLXNB2, SEMA4D is known to interact with or be associated with several other genes, including:

- **RHOA**: Involved in cytoskeletal dynamics and cellular migration.
- **PTK2B (PYK2)**: A tyrosine kinase involved in various cellular signaling pathways.
- **SRC**: A proto-oncogene that encodes a non-receptor tyrosine kinase.
- Other semaphorin family members, such as **SEMA3A** and **SEMA3B**, which may have genes that share functions in neuronal guidance and immune signaling.

### 2. Aging and Age-Related Diseases
Research has suggested potential roles of SEMA4D in aging and age-related diseases, particularly:

- **Neurodegenerative Diseases**: SEMA4D may influence synaptic health and neuron plasticity, implicating its potential role in neurodegenerative conditions such as Alzheimer's disease.
- **Inflammatory and Autoimmune Disorders**: Given its role in immune cell signaling and B-cell viability, disturbances in SEMA4D signaling have been implicated in some age-related inflammatory conditions.
- **Cardiovascular Health**: The promotion of endothelial cell migration suggests that changes in SEMA4D expression can affect age-related cardiovascular diseases, including atherosclerosis.

### 3. Drug Interactions
While direct pharmacological agents specifically targeting SEMA4D are not as well characterized, some classes of drugs may interact indirectly through pathways influenced by SEMA4D:

- **Immunomodulators**: Drugs that modulate immune responses could potentially affect SEMA4D functions due to its role in immune cell signaling.
- **Neurological Agents**: Medications acting on synaptic transmission may indirectly influence SEMA4D-related pathways, particularly in the context of neurodegenerative diseases.
- **Anticancer Agents**: Given that SEMA4D can influence cell migration and proliferation, certain oncology treatments targeting signaling pathways like AKT may indirectly impact SEMA4D function.

### 4. Pathways and Biological Processes
SEMA4D is involved in several critical pathways and biological processes:

- **Neuronal Guidance**: Plays a key role in the development and projection of neurons, influencing neuron connectivity.
- **Regulation of Immune Response**: Involved in the signaling processes that regulate B-cell aggregation, survival, and possibly the differentiation of immune cells.
- **Phosphatidylinositol 3-Kinase (PI3K) Signaling Pathway**: SEMA4D activates this pathway, which is crucial for cell growth and metabolism.
- **Cell Migration**: Impacts the migration of various cell types, including neuronal and endothelial cells.
- **GABAergic Synapse Development**: Involvement in the development of synapses which are critical for inhibitory neurotransmission.

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### Conclusion
The SEMA4D gene plays a multifaceted role in cellular signaling across neurons and immune cells. Its interactions with a variety of other genes and pathways underscore its significance in health and disease. Further research may elucidate its implications in aging and potential therapeutic targets.