MAPRE1 Human

What is MAPRE1 and what is its primary cellular function?

MAPRE1, also known as EB1, is a microtubule-associated protein that belongs to the RP/EB family. This 22919-gene encoded protein was first identified through its binding to the APC (Adenomatous polyposis coli) protein, which is frequently mutated in colorectal cancer . Its primary function involves regulation of microtubule dynamics and chromosome stability.

MAPRE1 localizes predominantly to microtubules, with particular concentration at growing ends in interphase cells. During mitosis, it associates with centrosomes and spindle microtubules . Due to its consistent localization at microtubule plus ends throughout the cell cycle, MAPRE1 is classified as a microtubule plus end tracking protein (+TIP protein) . This positioning is critical for its regulatory role in cytoskeletal organization and cellular stability.

The protein's interactions with components of the dynactin complex and cytoplasmic dynein intermediate chain suggest its involvement in multiple cytoskeletal regulatory pathways . These associations contribute to MAPRE1's central role in maintaining cellular structural integrity and ensuring proper chromosome segregation during cell division.

How does MAPRE1 contribute to microtubule dynamics?

MAPRE1 actively regulates microtubule dynamics through several distinct mechanisms. It promotes the elongation of CAMSAP2-decorated microtubule stretches specifically at the minus-end of microtubules . This regulatory function is essential for establishing and maintaining cellular polarity and organization.

Additionally, MAPRE1 functions downstream of Rho GTPases and DIAPH1 in the formation of stable microtubules . This pathway is critical for coordinated cytoskeletal responses to extracellular signals and may contribute to MAPRE1's potential role in cell migration processes . The protein also serves as a regulator of autophagosome transport through its interactions with CAMSAP2 , linking microtubule regulation to cellular degradation pathways.

During mitosis, MAPRE1's association with the centrosomes and spindle microtubules is particularly important for ensuring proper chromosome alignment and segregation . Its dysregulation can lead to chromosomal instability, potentially contributing to pathological processes including oncogenesis.

What are the recommended approaches for detecting MAPRE1 expression in human tissue samples?

For quantitative assessment of MAPRE1 expression at the transcript level, researchers should consider PCR-based approaches. PrimePCR SYBR Green Assays specific for MAPRE1 have been experimentally validated following MIQE guidelines (minimum information for publication of quantitative real-time PCR experiments) . These assays utilize primers designed to span introns, reducing the risk of genomic DNA amplification while ensuring representation of common transcript variants.

When performing PCR analysis, researchers should implement appropriate controls to ensure data validity:

• DNA contamination controls to assess genomic DNA presence

• Positive PCR controls to evaluate reaction performance

• RNA quality assays to determine RNA integrity

• Reverse transcription controls to assess cDNA synthesis efficiency

• Reference gene assays for normalization of expression data

For protein-level detection, ELISA kits specific for MAPRE1 are available with sensitivity ranges of approximately 0.057-0.058 ng/mL and detection ranges of 0.156-10 ng/mL . Immunofluorescence methods are also effective for visualizing MAPRE1's subcellular localization, particularly its association with microtubule plus ends, centrosomes, and mitotic spindles .

How can researchers effectively study MAPRE1's interactions with binding partners?

To investigate MAPRE1's protein-protein interactions, researchers should consider implementing a multi-faceted approach:

• Co-immunoprecipitation (Co-IP): This technique can identify interactions between MAPRE1 and known or suspected binding partners such as APC, components of the dynactin complex, and cytoplasmic dynein intermediate chain . Antibodies specific to MAPRE1 (often targeting the EB1 epitope) can be used to pull down protein complexes from cell lysates.

• Proximity-based labeling methods: BioID or APEX2-based approaches can identify proteins in close proximity to MAPRE1 in living cells, potentially revealing novel interaction partners without requiring stable associations.

• Fluorescence microscopy: Dual-color immunofluorescence microscopy can visualize the co-localization of MAPRE1 with potential binding partners, particularly at microtubule plus ends, centrosomes, and mitotic spindles . Super-resolution microscopy techniques provide enhanced spatial resolution for more precise co-localization analysis.

• Live-cell imaging with fluorescently tagged proteins: Expressing fluorescently tagged MAPRE1 alongside tagged versions of potential binding partners allows for dynamic analysis of their interactions throughout the cell cycle.

When selecting methodological approaches, researchers should consider the type of interaction being studied (stable vs. transient), subcellular localization constraints, and potential artifacts from overexpression systems.

How is MAPRE1 dysfunction linked to colorectal cancer development?

MAPRE1's connection to colorectal cancer stems primarily from its interaction with the APC protein, which is frequently mutated in both familial and sporadic forms of this malignancy . The relationship is complex and multifaceted:

MAPRE1 was first identified through its binding to APC, suggesting a functional relationship between these proteins in normal cellular processes . When APC is mutated in colorectal cancer, this interaction may be disrupted, potentially altering microtubule dynamics and chromosome stability - hallmarks of cancer development.

The protein's role in regulating microtubule structures and chromosome stability positions it as a potential contributor to genomic instability when dysregulated . Since MAPRE1 is essential for proper chromosome segregation during mitosis, its dysfunction could lead to chromosomal abnormalities commonly observed in colorectal cancers.

Research approaches to study this relationship should include:

• Analysis of MAPRE1 expression patterns in colorectal cancer tissues versus normal mucosa

• Assessment of the impact of common APC mutations on MAPRE1 binding and function

• Evaluation of MAPRE1's role in chromosomal stability in colorectal cancer cell models

• Investigation of the relationship between MAPRE1 expression levels and clinical outcomes in colorectal cancer patients

What is the evidence connecting MAPRE1 to neurodegenerative conditions?

MAPRE1 has been associated with Neuronopathy, Distal Hereditary Motor, Autosomal Dominant 7 , suggesting its potential involvement in neurological disorders. This connection likely relates to MAPRE1's critical role in microtubule dynamics, which is particularly important in neurons for maintaining cellular morphology and axonal transport.

The protein's role in regulating microtubule structures could be especially significant in neurons, where proper cytoskeletal organization is essential for maintaining axonal integrity and supporting efficient transport of cellular components over long distances. Disruption of these processes is a common feature in many neurodegenerative conditions.

MAPRE1's involvement in autophagosome transport through interaction with CAMSAP2 may also be relevant to neurodegeneration, as impaired autophagy is increasingly recognized as a contributor to neurodegenerative processes. Defects in cellular waste disposal mechanisms can lead to accumulation of protein aggregates and damaged organelles, which are hallmarks of many neurodegenerative diseases.

To further elucidate MAPRE1's role in neurodegeneration, researchers should consider:

• Analyzing MAPRE1 expression and localization in neuronal models and patient-derived samples

• Investigating the impact of MAPRE1 dysfunction on axonal transport processes

• Assessing how MAPRE1 variants affect autophagosome formation and transport in neuronal contexts

• Examining potential genetic associations between MAPRE1 variants and neurodegenerative disease risk

What approaches can be used to study MAPRE1's dynamic behavior at microtubule plus ends?

MAPRE1's function as a microtubule plus end tracking protein (+TIP) requires specialized techniques to capture its dynamic behavior. Advanced researchers should consider these methodological approaches:

• Live-cell imaging with fluorescently tagged MAPRE1: Expressing GFP-MAPRE1 fusion proteins allows visualization of its accumulation at growing microtubule plus ends, appearing as "comets" that move throughout the cell. This technique enables quantification of:

  • Growth rates of microtubule plus ends

  • Dwell time of MAPRE1 at microtubule tips

  • Recruitment dynamics of other +TIP proteins

• Single-molecule imaging: Using techniques like total internal reflection fluorescence (TIRF) microscopy with photoactivatable fluorescent proteins fused to MAPRE1 allows researchers to track individual molecules, revealing binding kinetics and residence times at microtubule ends.

• Fluorescence recovery after photobleaching (FRAP): By photobleaching MAPRE1 "comets" at microtubule plus ends and measuring fluorescence recovery, researchers can determine the exchange rate between microtubule-bound and cytoplasmic pools of the protein.

• In vitro reconstitution assays: Purified components including fluorescently labeled MAPRE1 and tubulin can be combined to reconstitute microtubule dynamics in controlled conditions, allowing direct observation of MAPRE1's effects on microtubule polymerization rates, catastrophe frequency, and rescue events.

These approaches should be complemented with perturbation studies using MAPRE1 mutants or inhibitors to establish causal relationships between MAPRE1 activity and observed microtubule behaviors.

How can researchers effectively model MAPRE1 dysfunction in cellular and animal systems?

Creating reliable models of MAPRE1 dysfunction requires careful consideration of the biological context and specific aspects of function being investigated:

• CRISPR/Cas9 genome editing: This approach allows precise modification of the endogenous MAPRE1 gene to create:

  • Complete knockout cell lines to study loss-of-function effects

  • Point mutations that disrupt specific protein interactions (e.g., with APC or microtubules)

  • Fluorescent protein knockins for live visualization at endogenous expression levels

• Inducible expression systems: Tetracycline-regulated expression of wild-type or mutant MAPRE1 enables temporal control, allowing researchers to study:

  • Acute versus chronic effects of MAPRE1 dysfunction

  • Dose-dependent phenotypes

  • Recovery dynamics after restoration of normal expression

• Animal models: While complete MAPRE1 knockout may be developmentally lethal, conditional knockout approaches can target specific tissues or developmental stages:

  • Floxed MAPRE1 alleles with tissue-specific Cre recombinase expression

  • Temporal control using tamoxifen-inducible Cre systems

  • CRISPR/Cas9-mediated mutation in model organisms

• Patient-derived cellular models: For studying disease-relevant phenotypes, researchers should consider:

  • iPSC-derived neurons from patients with MAPRE1-associated neurological disorders

  • Organoid cultures from colorectal cancer patients with altered MAPRE1 function

  • CRISPR/Cas9 correction of patient mutations to establish causality

When developing these models, researchers should implement appropriate validation steps, including verification of MAPRE1 expression levels, assessment of microtubule dynamics, and characterization of cellular phenotypes such as mitotic abnormalities or altered microtubule stability.

What are the emerging areas of investigation regarding MAPRE1's role beyond microtubule regulation?

Beyond its established functions in microtubule regulation, several emerging areas suggest broader roles for MAPRE1:

• Autophagy regulation: MAPRE1's function as a regulator of autophagosome transport through interaction with CAMSAP2 opens avenues for investigating its contribution to cellular quality control mechanisms. Researchers should explore how MAPRE1 coordinates microtubule dynamics with autophagosome formation, transport, and fusion with lysosomes.

• Cell migration: Evidence suggesting MAPRE1's involvement in cell migration processes warrants further investigation into its potential roles in:

  • Directional persistence during migration

  • Focal adhesion turnover

  • Coordination between actin and microtubule cytoskeletons during migration

• RNA binding: Gene Ontology annotations indicate RNA binding capability , suggesting potential roles in:

  • Localized translation at specific subcellular sites

  • RNA transport along microtubules

  • Post-transcriptional regulation of gene expression

• Signaling pathway integration: MAPRE1's position downstream of Rho GTPases and DIAPH1 suggests it may function as an integrator of extracellular signals with cytoskeletal responses. Investigation of how MAPRE1 activity is modulated by various signaling pathways could reveal new regulatory mechanisms.

These emerging areas highlight the need for integrated approaches combining traditional cell biology techniques with systems-level analyses to fully understand MAPRE1's multifaceted roles in cellular homeostasis.

How might therapeutic targeting of MAPRE1 be approached for cancer or neurological disorders?

Developing therapeutic strategies targeting MAPRE1 requires careful consideration of its essential cellular functions and disease-specific dysregulation:

• Cancer therapeutic approaches:

  • Disrupting specific interactions between MAPRE1 and oncogenic partners rather than targeting all MAPRE1 functions

  • Synthetic lethality approaches that exploit cancer-specific dependencies on MAPRE1

  • Combination therapies targeting MAPRE1 alongside microtubule-targeting agents to enhance efficacy or reduce resistance

• Neurological disorder interventions:

  • Gene therapy approaches to correct specific MAPRE1 mutations in hereditary conditions

  • Small molecules that stabilize MAPRE1 interactions with microtubules in conditions where these interactions are compromised

  • Targeting downstream effectors of MAPRE1 dysfunction that contribute to neurodegeneration

• Delivery challenges:

  • Development of blood-brain barrier-penetrant compounds for neurological applications

  • Cell-type specific targeting strategies to minimize off-target effects

  • Temporal control of interventions to address acute versus chronic aspects of disease

• Biomarker development:

  • Identification of MAPRE1 expression or modification patterns that predict disease progression

  • Development of imaging approaches to visualize MAPRE1 function in living tissues

  • Correlation of MAPRE1 status with treatment responses

Successful therapeutic development will require robust preclinical models that accurately recapitulate disease-specific alterations in MAPRE1 function, alongside medicinal chemistry approaches focused on achieving high specificity for disease-relevant interactions.