JPH4 Gene

JPH4 Gene

JPH4 — Junctophilin 4

Introduction

Jph4 Gene is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Junctophilin 4 (JPH4) is a member of the junctophilin family of proteins that play critical roles in bridging the plasma membrane with the endoplasmic reticulum (ER), facilitating calcium signaling in excitable cells. While less studied than its family members JPH1-3, JPH4 has emerged as a protein of interest in neuromuscular function and neurodegenerative diseases, particularly amyotrophic lateral sclerosis (ALS).

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Junctophilin 4</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>JPH4</td></tr>
<tr><td><strong>Full Name</strong></td><td>Junctophilin 4</td></tr>
<tr><td><strong>Chromosome</strong></td><td>14q11.2</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[128153](https://www.ncbi.nlm.nih.gov/gene/128153)</td></tr>
<tr><td><strong>OMIM</strong></td><td>612389</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000151148</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q8WXE8](https://www.uniprot.org/uniprot/Q8WXE8)</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Amyotrophic Lateral Sclerosis](/diseases/als), Neuromuscular Junction Defects</td></tr>
</table>
</div>

Overview

...

JPH4 Gene

JPH4 — Junctophilin 4

Introduction

Jph4 Gene is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Junctophilin 4 (JPH4) is a member of the junctophilin family of proteins that play critical roles in bridging the plasma membrane with the endoplasmic reticulum (ER), facilitating calcium signaling in excitable cells. While less studied than its family members JPH1-3, JPH4 has emerged as a protein of interest in neuromuscular function and neurodegenerative diseases, particularly amyotrophic lateral sclerosis (ALS).

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Junctophilin 4</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>JPH4</td></tr>
<tr><td><strong>Full Name</strong></td><td>Junctophilin 4</td></tr>
<tr><td><strong>Chromosome</strong></td><td>14q11.2</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[128153](https://www.ncbi.nlm.nih.gov/gene/128153)</td></tr>
<tr><td><strong>OMIM</strong></td><td>612389</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000151148</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q8WXE8](https://www.uniprot.org/uniprot/Q8WXE8)</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Amyotrophic Lateral Sclerosis](/diseases/als), Neuromuscular Junction Defects</td></tr>
</table>
</div>

Overview

JPH4 — Junctophilin 4 Junctophilin 4 (JPH4) is a member of the junctophilin family of proteins that play critical roles in bridging the plasma membrane with the endoplasmic reticulum (ER), facilitating calcium signaling in excitable cells.

Structure and Function

The junctophilin family consists of six members (JPH1-6) in mammals, characterized by a unique structure that allows them to anchor the endoplasmic reticulum to the plasma membrane^[1]. JPH4, like other junctophilins, contains:

• N-terminal membrane-repair (Membrane Occupation and Recognition Nexus, MORN) motifs (typically 6-8 repeats) that bind to phospholipids in the plasma membrane
• A central alpha-helical domain that spans the cytoplasmic space
• A C-terminal transmembrane domain that anchors the protein in the ER membrane

This architecture creates stable junctions between the sarcolemma (or plasma membrane) and the sarcoplasmic/endoplasmic reticulum, forming physical channels for rapid calcium release during excitation-contraction coupling^[2].

Tissue Distribution

JPH4 is predominantly expressed in:

• Skeletal muscle, particularly in fast-twitch muscle fibers
• Motor [neurons](/entities/neurons) in the spinal cord and brainstem
• Cardiac tissue at lower levels compared to JPH2
• Brain regions including the cerebral [cortex](/brain-regions/cortex) and cerebellum

The expression pattern suggests specialized roles in neuromuscular junctions and fast calcium signaling pathways^[3].

Role in Calcium Signaling

Junctophilins are essential for maintaining the structural integrity of calcium release units (CRUs) in muscle cells and neurons. At the neuromuscular junction, JPH4 participates in:

Synaptic vesicle organization: Maintaining the spatial arrangement of synaptic vesicles near calcium channels

Ryanodine receptor (RYR) clustering: Working with other junctophilins to organize ryanodine receptors at the sarcoplasmic reticulum

Voltage-gated calcium channel (VGCC) coupling: Facilitating physical coupling between VGCCs and RYR channels for efficient excitation-contraction coupling

Endoplasmic reticulum morphology: Contributing to the formation of junctional membrane complexes

Studies have shown that junctophilin knockout in skeletal muscle leads to severe myopathic changes due to disrupted calcium handling^[4].

Disease Associations

Amyotrophic Lateral Sclerosis (ALS)

JPH4 has been implicated in ALS pathogenesis through several mechanisms:

• Mutations in JPH4 have been identified in patients with familial ALS, suggesting a potential genetic contribution to disease susceptibility^[5]
• Dysregulated calcium homeostasis in motor neurons due to impaired junctophilin function may contribute to excitotoxicity — a key mechanism in ALS motor neuron degeneration
• Neuromuscular junction denervation — JPH4 dysfunction may accelerate the degeneration of neuromuscular junctions, a hallmark of ALS progression
• Mitochondrial dysfunction — Calcium dysregulation secondary to junctophilin impairment can lead to mitochondrial calcium overload and [apoptosis](/entities/apoptosis)

Neuromuscular Junction Defects

JPH4 is critical for maintaining the structural and functional integrity of the neuromuscular junction. Mutations or deficiencies can lead to:

• Impaired synaptic transmission
• Reduced quantal content at the neuromuscular junction
• Progressive muscle weakness
• Myopathic changes on muscle biopsy

Other Neurodegenerative Diseases

While most directly associated with ALS, JPH4 dysfunction may contribute to other neurodegenerative conditions characterized by calcium dysregulation:

• Spinal Muscular Atrophy (SMA): Disrupted neuromuscular junction integrity
• Peripheral Neuropathies: Impaired calcium signaling in peripheral nerves
• Alzheimer's Disease: Altered calcium homeostasis in neurons^[6]

Therapeutic Implications

Targeting JPH4 and related junctophilin pathways presents potential therapeutic opportunities:

Gene therapy approaches: Delivering functional JPH4 to restore calcium handling in motor neurons

Small molecule modulators: Developing compounds that enhance junctophilin function or stabilize junctional complexes

Calcium stabilizers: Using calcium channel modulators to compensate for impaired junctophilin function

Neuroprotective strategies: Targeting downstream effects of calcium dysregulation, such as mitochondrial dysfunction and excitotoxicity

Key Publications

Takeshima H, et al. (2000). "Junctophilins: a novel family of junctional membrane complex proteins." Mol Cell. PMID: 10678170(https://pubmed.ncbi.nlm.nih.gov/10678170/).

Ito K, et al. (2001). "Molecular architecture of the junctophilin involved in muscle Ca2+ signaling." Cell. PMID: 11719207(https://pubmed.ncbi.nlm.nih.gov/11719207/).

Nishi M, et al. (2003). "Expression and distribution junctophilin proteins in the nervous system." Neuroscience. PMID: 14521999(https://pubmed.ncbi.nlm.nih.gov/14521999/).

Hirata Y, et al. (2006). "Junctophilin deficiency induces mitochondrial dysfunction and necrosis in skeletal muscle." J Cell Sci. PMID: 16823086(https://pubmed.ncbi.nlm.nih.gov/16823086/).

Beccano-Kelly DA, et al. (2015). "Junctophilin-4: a new player in ALS pathogenesis?" Exp Neurol. [DOI:10.1016/j.expneurol.2015.02.025](https://doi.org/10.1016/j.expneurol.2015.02.025)

Bezprozvanny I. (2009). "Calcium signaling and neurodegenerative diseases." Trends Mol Med. PMID: 19758054(https://pubmed.ncbi.nlm.nih.gov/19758054/).

Background

The study of Jph4 Gene has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Amyloid Hypothesis](/mechanisms/amyloid-hypothesis)
• [Tau Pathology](/mechanisms/tau-pathology)
• [/mechanisms/app-processing](/mechanisms/app-processing)
• [/mechanisms/amyloid-aggregation](/mechanisms/amyloid-aggregation)

Cross-references

• [Amyotrophic Lateral Sclerosis](/diseases/als) — Primary disease association
• [Calcium Signaling](/mechanisms/calcium-signaling)mechanisms/calcium-signaling-dysregulation) — Primary mechanism
• [Neuromuscular Junction](/cell-types/neuromuscular-junction) — Site of function
• [Ryanodine Receptor](/ryanodine-receptor) — Interacting protein
• [Motor Neurons](/cell-types/motor-neurons) — Affected cell type
• [TDP-43](/proteins/tdp-43-protein) — ALS protein pathology
• [Excitotoxicity](/mechanisms/excitotoxicity) — Downstream mechanism
• [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction) — Downstream mechanism
• [Gene Database](/taxonomy?type=genes) — All gene pages

External Links

• [NCBI Gene: JPH4](https://www.ncbi.nlm.nih.gov/gene/128153)
• [UniProt: Q8WXE8](https://www.uniprot.org/uniprot/Q8WXE8)
• [Ensembl: ENSG00000151148](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000151148)
• [OMIM: 612389](https://www.omim.org/entry/612389)

References

^[1] Takeshima H, et al. (2000). "Junctophilins: a novel family of junctional membrane complex proteins." Molecular Cell. PMID: 10678170(https://pubmed.ncbi.nlm.nih.gov/10678170/). https://pubmed.ncbi.nlm.nih.gov/10678170/

^[2] Ito K, et al. (2001). "Molecular architecture of the junctophilin involved in muscle Ca2+ signaling." Cell. PMID: 11719207(https://pubmed.ncbi.nlm.nih.gov/11719207/). https://pubmed.ncbi.nlm.nih.gov/11719207/

^[3] Nishi M, et al. (2003). "Expression and distribution of junctophilin proteins in the nervous system." Neuroscience. PMID: 14521999(https://pubmed.ncbi.nlm.nih.gov/14521999/). https://pubmed.ncbi.nlm.nih.gov/14521999/

^[4] Hirata Y, et al. (2006). "Junctophilin deficiency induces mitochondrial dysfunction and necrosis in skeletal muscle." Journal of Cell Science. PMID: 16823086(https://pubmed.ncbi.nlm.nih.gov/16823086/). https://pubmed.ncbi.nlm.nih.gov/16823086/

^[5] Beccano-Kelly DA, et al. (2015). "Junctophilin-4: a new player in ALS pathogenesis?" Experimental Neurology. [DOI:10.1016/j.expneurol.2015.02.025](https://doi.org/10.1016/j.expneurol.2015.02.025) https://doi.org/10.1016/j.expneurol.2015.02.025

^[6] Bezprozvanny I. (2009). "Calcium signaling and neurodegenerative diseases." Trends in Molecular Medicine. PMID: 19758054(https://pubmed.ncbi.nlm.nih.gov/19758054/). https://pubmed.ncbi.nlm.nih.gov/19758054/