Recombinant Pongo abelii PDZK1-interacting protein 1 (PDZK1IP1)

What is PDZK1IP1 and what are its alternative names in scientific literature?

PDZK1IP1 (PDZK1-interacting protein 1) is a non-glycosylated membrane protein identified in the Golgi apparatus and plasma membranes . It is also known by several alternative names in scientific literature, including MAP17, DD96, and SPAP . The protein is encoded by the PDZK1IP1 gene and functions as a membrane-associated protein . In normal physiology, PDZK1IP1 is almost exclusively found in kidney epithelial cells in healthy human tissues, though its expression becomes dysregulated in various pathological conditions, particularly in cancers .

When designing experiments involving this protein, researchers should be careful to account for all possible nomenclature to ensure comprehensive literature searches and proper identification of the target protein. Experimental protocols should include validation steps using antibodies that specifically recognize PDZK1IP1 regardless of which name is used in the literature.

What is the structure and functional domain organization of PDZK1IP1?

The PDZK1IP1 protein in Pongo abelii consists of 114 amino acids containing a typical PDZK1IP1 (MAP17) superfamily domain . The amino acid sequence of the Pongo abelii PDZK1IP1 is:
MSAFGLLILGLLTAVPPASCRQGLGNLQPWMQGLIAVAVFLVLVAIAFAVNHFWCQEEPEPAHMILTIGNKADGVLVGTDGRYSSVAASFRSSEHENAYENVPEEEGKVRSTPM .

The protein contains structural features that enable its localization to the Golgi apparatus and plasma membranes. The expression region encompasses amino acids 1-114, representing the full-length protein . For experimental purposes, when working with recombinant PDZK1IP1, it's important to note that the tag type may vary during the production process and should be verified for each batch of protein .

Methodologically, researchers studying protein structure should consider using techniques such as X-ray crystallography or cryo-electron microscopy to fully elucidate the three-dimensional structure of PDZK1IP1, as detailed structural information remains limited in the current literature.

What is the genomic context and organization of the PDZK1IP1 gene?

The human PDZK1IP1 gene is located on chromosome 1 at position 1p33, specifically at coordinates NC_000001.11 (47183582..47190036, complement) according to recent genomic data . The gene contains a total of 4 exons . In comparison, the goat PDZK1IP1 gene consists of 345 base pairs, encoding a protein of 114 amino acids .

When designing gene expression studies or genetic manipulation experiments, researchers should account for the following methodological considerations:

• Primer design should target conserved regions across the 4 exons to ensure specific amplification

• When creating knockout or knockdown models, targeting multiple exons may increase efficiency

• For evolutionary studies, the relatively small size of the gene (approximately 6.5 kb in humans) makes it amenable to full-length sequencing and comparative genomics approaches

Researchers should utilize genome browsers and tools like Variation Viewer to examine PDZK1IP1 variants when studying genetic variations potentially associated with disease conditions .

How is PDZK1IP1 expression regulated in normal and pathological conditions?

Current research indicates that PDZK1IP1 expression is regulated at multiple levels:

• Transcriptional regulation: FXR1 (Fragile X-related protein 1) has been identified as a negative regulator of PDZK1IP1 at the mRNA level. FXR1 promotes PDZK1IP1 mRNA degradation by directly interacting with its 3′UTR region .

• Expression patterns in cancer: PDZK1IP1 shows variable expression across different cancer types. While high expression of PDZK1IP1 has been detected in many human carcinomas , downregulation of PDZK1IP1 has been documented in several tumor types, including esophageal cancer, laryngeal cancer, pancreatic cancer, oral squamous cell carcinoma, glioma, and prostate cancer .

Methodologically, researchers should employ multiple techniques to study PDZK1IP1 expression:

• qRT-PCR for mRNA quantification

• Western blotting and immunohistochemistry for protein detection

• RNA-seq for transcriptome-wide analysis

• ChIP-seq to identify transcription factors that regulate PDZK1IP1 expression

When interpreting expression data, researchers should consider tissue context and the potential influence of post-transcriptional regulatory mechanisms.

What methodologies are most effective for modulating PDZK1IP1 expression in experimental systems?

Based on current research approaches, several methodologies have proven effective for modulating PDZK1IP1 expression in experimental systems:

For overexpression studies:

• Plasmid-based expression systems have been successfully used to overexpress PDZK1IP1 in various cell lines, including cancer cells and preadipocytes .

• When designing overexpression experiments, researchers should consider including appropriate tags (e.g., FLAG, HA) for detection, while ensuring these tags do not interfere with protein function.

For knockdown/knockout studies:

• siRNA technology has been effectively employed to knockdown PDZK1IP1 expression. In goat subcutaneous preadipocytes, siRNA-mediated knockdown of PDZK1IP1 significantly inhibited cell proliferation .

• CRISPR-Cas9 system can be used for complete knockout of PDZK1IP1, though care must be taken to avoid off-target effects.

Efficiency assessment:

• For overexpression, EdU incorporation assays have been used to quantify changes in cell proliferation .

• Cell viability assays can measure functional consequences of PDZK1IP1 modulation .

• qRT-PCR should be used to verify successful alteration of PDZK1IP1 expression at the mRNA level.

• Western blotting should confirm changes at the protein level.

When designing experiments to modulate PDZK1IP1 expression, researchers should include appropriate controls and validate expression changes using multiple techniques. Time-course experiments may also be valuable to assess the dynamic effects of PDZK1IP1 modulation.

How does PDZK1IP1 influence cell proliferation at the molecular level?

PDZK1IP1 exerts significant effects on cell proliferation through multiple molecular mechanisms:

Regulation of cell cycle genes:
PDZK1IP1 modulates the expression of key cell cycle regulatory genes. In goat subcutaneous preadipocytes, overexpression of PDZK1IP1 upregulated mRNA expression of cell proliferation-associated genes including CCND1 (cyclin D1) and CDK2 (cyclin-dependent kinase 2) . Conversely, knockdown of PDZK1IP1 downregulated mRNA expression of cell proliferation-associated genes including CCNE1 (cyclin E1), CCND1, and CDK2 .

Impact on signaling pathways:

• PDZK1IP1 influences the phosphatidylinositol 3-kinase/Akt signaling pathway, keeping it active under certain conditions .

• PDZK1IP1 has been shown to suppress tumor necrosis factor-induced G1 arrest by downregulating p21 induction .

• PDZK1IP1 reduces c-Myc-mediated caspase3-like activity in Rat1 fibroblasts in low serum conditions .

Interaction with TGF-β signaling:
In lung adenocarcinoma models (NCI-H290 cells), increased PDZK1IP1 expression suppresses tumorigenicity caused by TGF-β signaling .

To investigate these molecular mechanisms, researchers should consider the following methodological approaches:

• Chromatin immunoprecipitation (ChIP) to identify direct interactions with promoter regions of cell cycle genes

• Co-immunoprecipitation to detect protein-protein interactions

• Phosphorylation analysis of signaling proteins (e.g., Akt, SMAD proteins) using phospho-specific antibodies

• Cell cycle analysis using flow cytometry following PDZK1IP1 modulation

• RNA-seq to identify global transcriptional changes induced by PDZK1IP1

What explains the contradictory roles of PDZK1IP1 in different cancer types?

One of the most intriguing aspects of PDZK1IP1 research is its apparently contradictory roles across different cancer types. Available data suggests several potential explanations for these context-dependent functions:

Tissue-specific molecular interactions:
PDZK1IP1 may interact with different binding partners depending on the tissue context. These tissue-specific interactions could determine whether PDZK1IP1 promotes or inhibits cancer progression.

Cancer-specific signaling pathway integration:

• In esophageal cancer (ESCA), low PDZK1IP1 expression was associated with advanced disease and poor prognosis, suggesting a tumor suppressor role .

• In contrast, high PDZK1IP1 expression has been detected in many carcinomas, suggesting potential oncogenic functions in these contexts .

Relationship to EMT (Epithelial-Mesenchymal Transition):
PDZK1IP1 appears to regulate EMT processes differently across cancer types:

• In oral squamous cell carcinoma (OSCC), PDZK1IP1 knockdown increased migration and metastasis both in vitro and in vivo .

• PDZK1IP1 overexpression leads to decreased levels of mesenchymal markers such as SLUG, N-cadherin, vimentin, Snail-2, Zeb-1, and SMAD2/3 .

To resolve these contradictions, researchers should:

• Use isogenic cell lines to control for genetic background

• Perform tissue-specific knockout studies in animal models

• Investigate the protein interactome of PDZK1IP1 across different tissue types

• Analyze epigenetic modifications that might influence PDZK1IP1 function

What are the optimal experimental approaches for studying PDZK1IP1's role in Epithelial-Mesenchymal Transition (EMT)?

Given PDZK1IP1's established involvement in regulating EMT processes, researchers investigating this relationship should consider the following experimental approaches:

In vitro methodologies:

• EMT marker analysis: Following PDZK1IP1 modulation, quantify changes in epithelial markers (E-cadherin) and mesenchymal markers (SLUG, N-cadherin, vimentin, Snail-2, Zeb-1) using Western blotting and immunofluorescence .

• Migration assays: Wound-healing and transwell migration assays to assess the functional impact of PDZK1IP1 on cellular motility .

• TGF-β response analysis: Since PDZK1IP1 interacts with TGF-β signaling, examine changes in SMAD2/3 phosphorylation and nuclear translocation following PDZK1IP1 modulation .

• 3D culture systems: Organoid cultures may better recapitulate in vivo EMT processes than traditional 2D cultures.

In vivo approaches:

• Metastasis models: Xenograft models combined with in vivo imaging to track metastatic spread following manipulation of PDZK1IP1 expression .

• Lineage tracing: In genetically engineered mouse models to track EMT in real-time with PDZK1IP1 modulation.

Molecular mechanistic studies:

• ChIP-seq: To identify direct transcriptional targets of EMT-related transcription factors following PDZK1IP1 modulation.

• RIME (Rapid Immunoprecipitation Mass Spectrometry of Endogenous Proteins): To identify PDZK1IP1 protein complexes during EMT.

• ATAC-seq: To examine chromatin accessibility changes at EMT-related gene loci.

When designing these experiments, researchers should consider:

How can researchers effectively design studies to explore the interaction between PDZK1IP1 and FXR1?

Recent research has identified an important regulatory relationship between FXR1 (Fragile X-related protein 1) and PDZK1IP1, where FXR1 negatively regulates PDZK1IP1 by promoting mRNA degradation via direct interaction with its 3′UTR . To further characterize this interaction, researchers should consider the following methodological approaches:

RNA-protein interaction studies:

• RNA immunoprecipitation (RIP): To confirm the binding of FXR1 to PDZK1IP1 mRNA in various cell types.

• Cross-linking immunoprecipitation (CLIP): For more precise mapping of FXR1 binding sites on PDZK1IP1 mRNA.

• RNA Electrophoretic Mobility Shift Assay (REMSA): To assess direct binding and binding affinity between purified FXR1 protein and PDZK1IP1 mRNA fragments.

mRNA stability assays:

• Actinomycin D chase experiments: To measure PDZK1IP1 mRNA half-life in the presence and absence of FXR1.

• Luciferase reporter assays: Using constructs containing the PDZK1IP1 3′UTR to quantify the effect of FXR1 on post-transcriptional regulation.

Functional rescue experiments:

• Design experiments where PDZK1IP1 is overexpressed in FXR1-overexpressing cells to determine if the phenotypic effects of FXR1 can be reversed .

• Utilize PDZK1IP1 constructs lacking the 3′UTR to determine if they are resistant to FXR1-mediated degradation.

In vivo validation:

• Xenograft models comparing tumor formation in:

  • Control cells

  • FXR1-overexpressing cells

  • PDZK1IP1-overexpressing cells

  • Cells with combined FXR1 and PDZK1IP1 overexpression

The results from the combination of these approaches would provide comprehensive insights into the molecular mechanisms and functional significance of the FXR1-PDZK1IP1 regulatory axis in normal and pathological conditions.