pih1d1 Antibody

What is PIH1D1 and why is it significant in research?

PIH1D1 (PIH1 Domain Containing 1) functions as a multipoint scaffold protein within the R2TP complex, coupling the Rvb1-Rvb2 hetero-dodecamer, the Hsp90 chaperone machinery (via Tah1 in yeast or Spagh/RPAP3 in metazoa), and the TTT (Tel2-Tti1-Tti2) complex. This makes it crucial for the activation and stabilization of PIKKs (phosphatidylinositol 3-kinase-related kinases). The protein contains specific domains that mediate important protein-protein interactions, including a PIH domain that recruits client proteins and a CS domain involved in protein binding. Understanding PIH1D1's role in cellular processes provides insights into fundamental mechanisms of protein complex assembly and cellular signaling pathways .

What types of PIH1D1 antibodies are available for research purposes?

Research-grade PIH1D1 antibodies are predominantly available as rabbit polyclonal antibodies, though some mouse monoclonal options exist. Common variants include antibodies targeting specific regions of the protein, such as C-terminal antibodies (like ABIN2790671) or those recognizing the full-length protein (AA 1-290). These antibodies vary in their form, including affinity-purified immunoglobulins in buffered aqueous solutions or buffered aqueous glycerol solutions. Most available antibodies demonstrate reactivity to human PIH1D1, with some showing cross-reactivity with other species including rat, cow, dog, guinea pig, horse, and rabbit with varying degrees of sequence homology .

How do PIH1D1 antibodies differ in their target epitopes?

PIH1D1 antibodies target different epitopes based on their design and intended application. Some antibodies, like the C-terminal targeting antibody ABIN2790671, are directed toward a synthetic peptide sequence "GLSLEIGENR LVMGGPQQLY HLDAYIPLQI NSHESKAAFH RKRKQLMVAM" at the C-terminal region of human PIH1D1. Other antibodies target the N-terminal region or the full-length protein. The epitope selection significantly impacts cross-reactivity with different species, with predicted reactivity ranging from 79% in cows to 100% in humans for certain antibodies. The epitope choice also influences the antibody's utility in different experimental applications based on whether the target region remains accessible in native or denatured protein conformations .

What are the validated applications for PIH1D1 antibodies?

PIH1D1 antibodies have been validated for multiple applications with specific working concentrations for each technique. Western blotting is the most commonly validated application, with working concentrations ranging from 0.04-0.4 μg/mL for high-sensitivity antibodies like HPA047258 to approximately 1 μg/mL for others. Immunohistochemistry applications typically use dilutions between 1:200-1:500, particularly with antibodies that have been extensively validated through human tissue arrays including 44 normal tissues and common cancer types. Immunofluorescence typically requires 0.25-2 μg/mL concentration, while immunoprecipitation has been validated for select antibodies. Additionally, ELISA has been confirmed as a viable application for several PIH1D1 antibodies .

How should I optimize western blotting protocols when using PIH1D1 antibodies?

For optimal western blotting results with PIH1D1 antibodies, begin with the manufacturer's recommended concentration (typically 0.04-1 μg/mL depending on the specific antibody). The PIH1D1 protein runs at approximately 32-36 kDa on SDS-PAGE gels, so ensure your gel percentage and running conditions allow clear resolution in this range. Standard blocking with 5% non-fat milk or BSA in TBST is typically sufficient, but optimization may be required for specific antibodies. For detection, both chemiluminescence and fluorescence-based secondary antibody systems work effectively. When troubleshooting, consider that denaturation conditions may affect epitope accessibility, particularly for conformational epitopes, and adjust your sample preparation accordingly. If non-specific bands appear, increasing antibody dilution or extending wash steps often improves specificity .

What considerations are important when using PIH1D1 antibodies for immunohistochemistry?

When employing PIH1D1 antibodies for immunohistochemistry, tissue fixation and antigen retrieval methods significantly impact staining quality. Most validated protocols for PIH1D1 antibodies utilize formalin-fixed paraffin-embedded tissues with heat-induced epitope retrieval using citrate buffer (pH 6.0) or EDTA buffer (pH 9.0). The recommended dilution range for PIH1D1 antibodies in IHC applications is typically between 1:200-1:500, but this should be empirically determined for each tissue type and fixation method. Inclusion of positive control tissues with known PIH1D1 expression and negative controls (primary antibody omitted) is essential for result interpretation. For multiplexing experiments, consider that PIH1D1 localizes primarily to the nucleus and cytoplasm, making it compatible with markers for other cellular compartments. Additionally, for phosphorylation-specific studies, phosphatase inhibitors should be included during tissue processing to preserve phosphorylation-dependent interactions of PIH1D1 .

How does phosphorylation affect PIH1D1's molecular interactions?

Phosphorylation plays a critical role in regulating PIH1D1's molecular interactions, particularly through its PIH domain. Structural and biochemical analyses reveal that the PIH domain in PIH1D1 specifically recognizes and binds to casein kinase 2 (CK2) phosphorylation sites in target proteins such as Tel2. This phosphorylation-dependent interaction is essential for the recruitment of the TTT (Tel2-Tti1-Tti2) complex to the R2TP complex. The structural basis for this interaction involves specific recognition of phosphorylated residues within Tel2 by the PIH domain of PIH1D1. When designing experiments to study these interactions, researchers should consider the phosphorylation state of potential binding partners and include phosphatase inhibitors in lysate preparation to preserve these transient interactions. Additionally, when using PIH1D1 antibodies to study these interactions, it's crucial to verify that the antibody epitope doesn't overlap with or affect the phosphopeptide-binding region of the PIH domain .

What is known about the structural organization of PIH1D1 and how does it impact experimental design?

PIH1D1 contains distinct structural domains that mediate its scaffold function in the R2TP complex. The N-terminal region contains the PIH domain, which specifically binds CK2-phosphorylated motifs in proteins like Tel2. The central region mediates interaction with the Rvb1-Rvb2 hetero-dodecamer in a constitutive and direct manner. The C-terminal CS domain interacts with regions of binding partners like RPAP3/Tah1. When designing experiments to study domain-specific functions, researchers should consider using domain-specific antibodies or generating constructs expressing individual domains. For co-immunoprecipitation studies, antibodies targeting regions not involved in protein-protein interactions should be selected to avoid disrupting complexes. Understanding that PIH1D1 serves as a multipoint scaffold helps explain why certain experimental approaches might disrupt some interactions while preserving others. Structural information should inform the design of mutation studies, particularly when investigating the functional consequences of disrupting specific protein-protein interactions .

How does PIH1D1 function within the R2TP complex and what implications does this have for experimental studies?

PIH1D1 functions as the central scaffold of the R2TP complex, mediating multiple protein-protein interactions. It couples the Rvb1-Rvb2 hetero-dodecamer with the Hsp90 chaperone machinery (via Tah1 in yeast or Spagh/RPAP3 in metazoa) and the TTT (Tel2-Tti1-Tti2) complex. Its interaction with Rvb1-Rvb2 appears constitutive and direct, requiring a central region of PIH1D1, while its interaction with TTT is mediated by a CK2-phosphorylated motif in Tel2 and the N-terminal PIH domain of PIH1D1. When studying PIH1D1 experimentally, these complex interactions necessitate careful consideration of buffer conditions, as high salt concentrations might disrupt some interactions. Additionally, when performing immunoprecipitation studies, researchers must consider the potential competitive binding between various partners at overlapping binding sites. For studying dynamic complex assembly, researchers might employ size-exclusion chromatography combined with multi-angle light scattering to characterize complex formation under different conditions. The scaffold nature of PIH1D1 also suggests that its depletion would have pleiotropic effects, complicating the interpretation of knockdown or knockout studies .

What approaches can resolve non-specific binding issues with PIH1D1 antibodies?

When encountering non-specific binding with PIH1D1 antibodies, several strategic approaches can improve specificity. First, optimize blocking conditions by testing different blocking agents (BSA, non-fat milk, normal serum) at various concentrations (3-5%) and incubation times (1-2 hours at room temperature or overnight at 4°C). Second, increase antibody dilution beyond the manufacturer's recommendation, as most PIH1D1 antibodies demonstrate acceptable signal-to-noise ratios at dilutions between 1:500-1:2000 for Western blotting. Third, implement more stringent washing steps by increasing the number of washes (5-6 times), duration (10 minutes each), and detergent concentration (up to 0.1% Tween-20) in wash buffers. Fourth, pre-absorb the antibody with non-relevant proteins by incubating with non-target tissue lysate before application to your sample. Finally, verify antibody specificity using appropriate controls, including PIH1D1 knockout/knockdown samples and pre-incubation with immunizing peptide when available. These systematic approaches typically resolve most non-specific binding issues with PIH1D1 antibodies .

How can I determine the optimal antibody for studying PIH1D1 interactions with specific binding partners?

Selecting the optimal PIH1D1 antibody for studying specific protein-protein interactions requires careful consideration of epitope location relative to interaction domains. For studying PIH1D1 interactions with Tel2 and the TTT complex, choose antibodies targeting regions outside the N-terminal PIH domain, as this domain mediates the phosphorylation-dependent interaction with Tel2. For investigating interactions with Rvb1-Rvb2, avoid antibodies targeting the central region of PIH1D1. When studying interactions with Hsp90 machinery via Tah1/RPAP3, avoid antibodies targeting the CS domain of PIH1D1. Perform preliminary co-immunoprecipitation assays with different antibodies to identify those that preserve the interaction of interest. Consider epitope accessibility within protein complexes, as some epitopes may become masked when PIH1D1 engages with binding partners. For studying dynamic complexes, combining different antibodies targeting non-overlapping epitopes can provide complementary information. Additionally, cross-validate findings using reverse co-immunoprecipitation with antibodies against the binding partner of interest .

What factors might affect reproducibility in experiments using PIH1D1 antibodies?

Multiple factors can impact reproducibility when working with PIH1D1 antibodies. Lot-to-lot variability in antibody production can introduce inconsistencies, making it advisable to purchase sufficient quantities from a single lot for long-term projects. Cell culture conditions significantly affect PIH1D1 expression and complex formation; maintain consistent cell density, passage number, and growth conditions across experiments. PIH1D1's involvement in phosphorylation-dependent interactions means that sample handling affects results; consistently use phosphatase inhibitors during sample preparation and standardize the time between cell lysis and antibody incubation. Experimental conditions including buffer composition, incubation temperatures, and incubation times should be precisely controlled and documented. For immunohistochemistry applications, tissue fixation protocols and antigen retrieval methods must be standardized. When comparing results between different PIH1D1 antibodies, differences in epitope specificity can lead to seemingly contradictory results, especially if studying phosphorylation-dependent interactions or conformationally sensitive regions .

How does the PIH domain in PIH1D1 specifically recognize phosphorylated substrates?

The PIH domain in PIH1D1 contains a specialized binding pocket that specifically recognizes CK2-phosphorylated motifs in target proteins like Tel2. Structural and biochemical analyses reveal that this domain demonstrates high specificity for phosphorylated serine/threonine residues within particular sequence contexts. The binding mechanism involves direct interactions between positively charged amino acids in the PIH domain and the negatively charged phosphate group on substrate proteins. This phosphorylation-dependent interaction is essential for the recruitment of client proteins to the R2TP complex. When designing experiments to study these interactions, researchers should consider that dephosphorylation of the target substrate would abolish the interaction, making phosphatase inhibitors crucial during experimental procedures. Additionally, mutations in key residues within the PIH domain's phosphopeptide-binding pocket would disrupt client protein recognition without affecting other functions of PIH1D1, providing a useful experimental approach for dissecting domain-specific functions .

What is known about the interaction between PIH1D1 and the Hsp90 chaperone system?

The interaction between PIH1D1 and the Hsp90 chaperone system is mediated through adaptor proteins - Tah1 in yeast or Spagh/RPAP3 in metazoa. In the crystal structure of the Hsp90-Tah1-Pih1 complex, Tah1 acts as the bridging component, with its TPR domain binding to the C-terminal MEEVD motif of Hsp90 while its C-terminal region interacts with the CS domain of Pih1 (PIH1D1). Interestingly, two molecules of Tah1 can bind to an Hsp90 dimer, occupying both C-terminal binding sites. This binding arrangement prevents the formation of mixed Hsp90-TPR domain cochaperone complexes, as demonstrated by competition assays where increasing concentrations of another TPR-domain cochaperone (Cpr6) progressively decreased the levels of C-Hsp90 co-immunoprecipitated by FLAG-Tah1. For researchers studying these interactions, this suggests that the stoichiometry and composition of Hsp90-cochaperone complexes are important considerations, and that competitive binding assays can provide insights into the dynamics of complex formation involving PIH1D1 .

How does the evolutionary conservation of PIH1D1 inform cross-species research approaches?

The evolutionary conservation of PIH1D1 provides valuable insights for cross-species research approaches. PIH1D1 shows varying degrees of sequence homology across species, with predicted reactivity ranging from 79% in cows to 100% in humans for certain epitopes. This conservation pattern suggests that functionally important domains, such as the PIH domain and CS domain, are likely to be more highly conserved than less functionally constrained regions. When selecting antibodies for cross-species studies, researchers should prioritize those targeting highly conserved epitopes. For functional studies across species, expected conservation of protein-protein interactions should be evaluated through sequence alignment and structural prediction of interaction interfaces. When interpreting results from model organisms, researchers should consider that while core functions of PIH1D1 are likely conserved, species-specific differences in regulation or auxiliary interactions may exist. Phylogenetic analysis using methods like CLUSTALW/MUSCLE within MEGA7 can help identify evolutionary relationships and functional conservation. This approach facilitates the translation of findings between model systems and human studies, particularly for fundamental aspects of PIH1D1 function in the R2TP complex .