GO:0035610 protein side chain deglutamylation

Protein side chain deglutamylation (GO:0035610) is a biological process that removes glutamate residues from the side chains of proteins, thereby reversing polyglutamylation, a post-translational modification that adds glutamate chains to the gamma-carboxyl group of glutamate residues within the primary protein sequence. This process is critical for regulating protein function, particularly in the nervous system, where polyglutamylation levels must be tightly controlled. The discovery of a family of deglutamylating enzymes, including CCP1-CCP6, has shed light on how cells maintain the dynamic balance of this modification. Researchers study protein side chain deglutamylation because its dysregulation leads to severe pathologies. For instance, mutations in CCP1 cause neurodegeneration in mice, characterized by Purkinje cell loss and ataxia. Additionally, CCP1 deficiency results in subfertility due to reduced numbers of antral follicles in female mice. More recently, CCP6 has been implicated in centrosome organization and cilium assembly, linking deglutamylation to fundamental cellular processes. Understanding this process at the molecular level is essential for developing therapeutic strategies for related diseases. The importance of GO:0035610 extends beyond basic biology. It serves as a paradigm for how post-translational modifications are reversed to control protein stability, localization, and interactions. With the advent of CRISPR gene editing, researchers can now create precise models to study the roles of individual deglutamylases in vivo and in vitro, accelerating discoveries in neurobiology, reproductive biology, and ciliary biology [1,2,3].

Protein side chain deglutamylation (GO:0035610) is defined as the removal of a glutamate residue from the side chain of a protein. Glutamate side chains are added to glutamic acid residues within the primary protein sequence during polyglutamylation, and deglutamylation reverses this modification. This process is catalyzed by enzymes known as deglutamylases, which are members of the cytosolic carboxypeptidase family.

Protein side chain deglutamylation is crucial for maintaining cellular homeostasis by reversing polyglutamylation, a modification that regulates protein interactions and stability. Its importance is underscored by the fact that mutations in deglutamylating enzymes cause severe neurological and reproductive defects in animal models [1,3]. Furthermore, the involvement of CCP6 in centrosome and cilia function highlights its broader significance in cell biology. Studying this process provides insights into fundamental mechanisms of post-translational regulation and offers potential therapeutic targets for related diseases.

The following genes encode enzymes or related proteins that directly participate in or regulate protein side chain deglutamylation (GO:0035610).

The activity of deglutamylating enzymes is regulated at multiple levels. Transcriptional control of CCP1 and other family members can influence their abundance in specific tissues. Post-translational modifications, such as phosphorylation, may modulate their enzymatic activity, although direct evidence is limited. Additionally, the availability of polyglutamylated substrates and interacting proteins, such as those identified for CCP6 in centrosome organization, can affect the efficiency of deglutamylation. Hormonal regulation may also play a role, as CCP1 deficiency leads to subfertility with reduced antral follicles, suggesting endocrine involvement.

Mutations in CCP1 (AGTPBP1) cause progressive neurodegeneration in mice, characterized by Purkinje cell loss and ataxia. This links defective deglutamylation to neuronal death, highlighting the importance of this process for brain function. Human patients with AGTPBP1 mutations may present with similar neurodegenerative phenotypes, although further studies are needed.

Female mice lacking CCP1 exhibit subfertility due to a reduced number of antral follicles, indicating that deglutamylation is essential for normal ovarian function. This suggests that dysregulation of protein side chain deglutamylation could contribute to reproductive disorders in humans, though direct evidence is still emerging.

CCP6 is associated with centrosome organization and cilium assembly, processes that are disrupted in ciliopathies. Proximity mapping studies have revealed interactions with centrosomal and ciliary proteins, suggesting that impaired deglutamylation may contribute to developmental defects and diseases such as Meckel syndrome.

Mass spectrometry-based proteomics can identify and quantify polyglutamylation levels on target proteins, allowing researchers to assess the impact of deglutamylation enzymes. This method is essential for discovering novel substrates and mapping modification sites.

Fluorescence microscopy and proximity labeling techniques, such as BioID, can visualize the localization of deglutamylases and their interactions with cellular structures like the centrosome and cilia. These approaches provide spatial and temporal insights into the process.

CRISPR knockout or activation screens can systematically test the function of deglutamylase family members and identify genetic interactions [1,2]. Such screens are powerful for uncovering redundant pathways and novel regulators.

Mouse models with mutations in CCP1 (e.g., pcd3J-/-) have been instrumental in linking deglutamylation to neurodegeneration and subfertility [1,3]. Phenotypic analysis, including histology and behavioral tests, reveals the physiological consequences of impaired deglutamylation.

Researchers studying protein side chain deglutamylation-related genes often need to determine whether a candidate gene is causally involved in the process or merely correlated with it. EDITGENE provides a comprehensive suite of CRISPR services to generate precisely engineered cell and animal models, enabling rigorous functional validation of deglutamylases and their substrates.

Protein side chain deglutamylation (GO:0035610) is a fundamental biological process that reverses polyglutamylation, a modification critical for protein function. The cytosolic carboxypeptidase family, including CCP1 and CCP6, plays central roles in this process, with mutations leading to neurodegeneration, subfertility, and ciliary defects [1,2,3]. Understanding the molecular mechanisms and regulation of deglutamylation offers insights into disease pathogenesis and potential therapeutic avenues. CRISPR-based models are indispensable for dissecting these pathways and validating candidate genes.