EIF3F Human

What is the molecular structure of human EIF3F?

Human eIF3f is a 47 kDa protein (in denaturing electrophoresis conditions) with a deduced molecular mass of 38.5 kDa based on its amino acid sequence. This discrepancy is attributed to the high proline content in its N-terminal region. The protein contains a characteristic proline- and alanine-rich N-terminal region that appeared during the amniote clade evolution and is not required for all of its functional interactions . Researchers studying eIF3f should note this anomalous migration pattern when performing Western blot analysis to correctly identify the protein.

What are the primary cellular functions of EIF3F in humans?

EIF3F functions as a component of the eIF3 complex involved in protein synthesis, but also has independent roles in several cellular processes. In human cells, eIF3f is involved in cell cycle regulation and proliferation, with expression peaks during G1/S and G2/M phases . It participates in protein synthesis control, DNA repair mechanisms, and signal transduction pathways. When studying eIF3f functions, researchers should consider its dual role as both part of the eIF3 complex and as an independent functional protein with distinct interaction partners.

How is EIF3F expression regulated in different human tissues?

EIF3F exhibits a fluctuating expression pattern in cycling cells, with maximum expression peaks in G1/S and G2/M phases . Its expression varies across tissue types, and altered expression has been reported in several human tumors, being downregulated in some cell lines and upregulated in others . For tissue-specific studies, researchers should establish baseline expression levels in their target tissues before examining experimental interventions or disease states.

What protein-protein interactions have been confirmed for EIF3F?

EIF3F forms a stable physical interaction with the alpha 1B-adrenergic receptor (α1B-ADR), a plasma membrane protein involved in vasoconstriction and cell proliferation . This complex of approximately 120 kDa has been identified in multiple human and mouse cell lines (A549, HepG2, Ramos, and MC3T3-E1), suggesting the interaction is conserved in mammals and is not tissue-specific . When studying eIF3f interactions, co-immunoprecipitation under native conditions is recommended to preserve these complexes, as demonstrated in the literature with antibodies against both eIF3f and α1B-ADR.

How does EIF3F affect adrenergic receptor signaling pathways?

Upon catecholamine stimulation, eIF3f promotes adrenoceptor activity by enhancing GTP binding to Gαq/11, a key step in the signal transduction pathway . Interestingly, the proline- and alanine-rich N-terminal region of eIF3f is not required for this adrenoceptor activation, and truncated eIF3f (lacking this region) actually stimulates more GTP binding, suggesting this domain may lower its affinity for the adrenoceptor . Researchers studying this interaction should consider using radiolabeled [γ-32P]GTP transfer assays to measure adrenoceptor activity in the presence or absence of eIF3f.

What is the relationship between EIF3F and the MTOR pathway?

Studies in mice indicate that partial depletion of eIF3f amplifies muscle atrophy compared to wild-type mice and reduces MTOR pathway activation . This suggests a potential role for eIF3f in modulating the MTOR signaling pathway, which regulates protein synthesis and cell growth. Researchers investigating this relationship should consider examining phosphorylation states of MTOR pathway components (such as S6K and 4E-BP1) in models with altered eIF3f expression.

What are the clinical manifestations of EIF3F-related neurodevelopmental disorders?

EIF3F-related neurodevelopmental disorders (NDDs) are characterized by global developmental delay, delayed speech development, behavioral difficulties, altered muscular tone, and hearing loss . Motor milestone delays are common, with 33% of affected individuals exhibiting delays in unassisted sitting and 70% showing delays in independent walking . Hearing loss affects approximately 57% of patients, and behavioral problems such as obsessive-compulsory disorder, social problems, anxiety, autism, hyperactivity, and attention deficit are observed in 57% of cases . Researchers studying these disorders should use standardized developmental assessments to characterize phenotypes consistently.

How do EIF3F mutations contribute to pathogenesis in neurodevelopmental disorders?

EIF3F mutations likely cause neurodevelopmental disorders through loss-of-function mechanisms. Supporting evidence comes from murine studies where partial depletion of eIF3f amplified muscle atrophy and reduced MTOR pathway activation . The mutations may disrupt protein synthesis regulation and other cellular processes critical for normal neurodevelopment. For researchers investigating pathogenic mechanisms, genome-wide sequencing approaches (genome or exome sequencing) are essential for diagnostic work-up, as brain imaging does not reveal specific diagnostic findings in EIF3F-related NDDs .

Is there evidence linking EIF3F to oncogenesis?

Yes, several lines of evidence suggest a potential role for eIF3f in cancer development. First, altered expression of eIF3f has been reported in several human tumors, being downregulated in some cell lines and upregulated in others . Second, eIF3f interacts with α1B-ADR, which is considered a proto-oncogene . Third, eIF3f's involvement in cell cycle regulation, particularly at G1/S and G2/M transitions, suggests it may influence cell proliferation control . Researchers examining eIF3f in cancer contexts should consider analyzing both gene expression levels and protein-protein interactions, particularly with known oncogenes.

What are effective approaches for detecting EIF3F-protein interactions?

To identify and characterize eIF3f-protein interactions, several complementary approaches are recommended:

• Native gel electrophoresis followed by immunoblotting can preserve protein complexes for initial detection .

• Co-immunoprecipitation with specific antibodies against eIF3f or suspected interaction partners, followed by SDS-PAGE and either immunoblotting or N-terminal sequencing .

• Proximity labeling techniques as mentioned in search result .

• Mass spectrometry-based approaches for unbiased identification of interaction partners.

Researchers should be aware that some interactions may be lost under denaturing conditions, necessitating native buffers that respect protein conformation and protein-protein interactions.

How can researchers effectively study EIF3F function in cellular models?

To study eIF3f function in cellular models, researchers can employ:

• Transient expression analysis to examine effects of eIF3f deregulation on cell viability and apoptosis .

• siRNA or CRISPR-based approaches for loss-of-function studies.

• Overexpression systems to evaluate gain-of-function effects.

• Cell cycle synchronization to study eIF3f's fluctuating expression pattern during different phases .

• Functional assays specific to suspected pathways, such as the [γ-32P]GTP transfer assay for adrenoceptor activation .

When designing these studies, researchers should consider cell type-specific effects, as eIF3f functions may vary across different cellular contexts.

What quantitative techniques are recommended for EIF3F protein analysis?

For quantitative analysis of eIF3f, search result describes label-free quantification using mass spectrometry with the SafeQuant R package for normalization and statistical analysis. This approach includes quantification of total peak/reporter areas, summation of peak areas per protein, and calculation of protein abundance ratios . For normalization, researchers studying core eIF3f-eIF3 interactions can normalize against protein abundances of specific subunits (EIF3A, EIF3CL, EIF3E, EIF3F, and EIF3H) rather than using global normalization . Statistical testing of differential protein expression between conditions can be performed using empirical Bayes moderated t-tests, with p-values adjusted for multiple testing using the Benjamini-Hochberg method .

How do researchers reconcile contradictory findings regarding EIF3F expression in cancer?

The literature reports contradictory findings regarding eIF3f expression in cancer, with some studies showing downregulation and others showing upregulation . To address these contradictions, researchers should:

• Carefully define the specific cancer type, stage, and cell line being studied

• Use multiple detection methods (qPCR, Western blot, immunohistochemistry)

• Examine both mRNA and protein levels, as post-transcriptional regulation may occur

• Consider the broader context of eIF3f interactions, particularly with proto-oncogenes like α1B-ADR

• Analyze pathway-specific effects rather than just expression levels

• Account for potential tissue-specific roles of eIF3f

These contradictory results suggest eIF3f may have context-dependent roles in different cancer types or stages, possibly functioning as both a tumor suppressor and oncogene depending on cellular context.

What are the challenges in studying EIF3F's dual role in translation and signal transduction?

Studying eIF3f's dual role presents several methodological challenges:

• Distinguishing eIF3f's activities as part of the eIF3 complex versus its independent functions

• Identifying which protein domains are responsible for specific interactions and functions

• Determining whether certain functions are cell type-specific or universal

• Assessing how alterations in one function (e.g., translation) affect other functions (e.g., adrenoceptor activation)

• Developing experimental designs that can isolate specific pathways without disrupting others

Researchers should consider using domain-specific mutations or truncations, as demonstrated with the N-terminal region studies , and employ pathway-specific activity assays to differentiate between eIF3f's various functions.

What emerging technologies show promise for advancing EIF3F research?

Emerging technologies that may advance eIF3f research include:

• Proximity labeling techniques (mentioned in ) for identifying transient or context-specific interactions

• CRISPR-based gene editing for creating precise mutations that mimic those found in neurodevelopmental disorders

• Single-cell analysis to examine cell-to-cell variability in eIF3f expression and function

• Cryo-electron microscopy for structural studies of eIF3f within protein complexes

• Ribosome profiling to assess translation-specific functions

• Phosphoproteomics to identify post-translational modifications that regulate eIF3f activity

These technologies offer opportunities to address current knowledge gaps and resolve contradictions in the literature regarding eIF3f functions.