Inhibin alpha A Chain Human
Description
Definition and Molecular Structure
The Inhibin alpha A chain (encoded by the INHA gene on human chromosome 2) is a polypeptide that combines with a beta subunit (βA or βB) to form inhibin A or B, respectively . Mature Inhibin A is a disulfide-linked heterodimer, with the alpha subunit weighing ~18 kDa and the beta subunit ~13 kDa . Recombinant human Inhibin alpha A chains are produced in E. coli as non-glycosylated polypeptides containing 134 amino acids (residues 233–366) with an N-terminal hexahistidine tag .
Hormonal Regulation
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FSH Suppression: Inhibin A inhibits pituitary follicle-stimulating hormone (FSH) secretion by antagonizing activin signaling via ActRIIA/ActRIIB receptors .
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Gonadal Function: Regulates granulosa and Sertoli cell proliferation, impacting gametogenesis and steroidogenesis .
Tumor Suppression
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Inhibin alpha exhibits tumor-suppressor activity in gonadal and adrenal tissues. Loss of INHA expression correlates with malignancies like adrenocortical carcinoma (ACC) and prostate cancer .
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In melanoma and leukemia, promoter hypermethylation silences INHA, contributing to tumor progression .
Extragonadal Roles
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Expressed in placental syncytiotrophoblasts, Inhibin A modulates GnRH, hCG, and progesterone secretion during pregnancy .
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Thecal cells in ovaries also secrete free alpha subunits, influencing androgen production and follicular dynamics .
Biomarker Potential
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Serum inhibin A levels are markers for granulosa cell tumors and placental health .
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Pro-αC (a precursor form) is elevated in ACC, serving as a diagnostic tool .
Therapeutic Implications
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Demethylating agents (e.g., 5-Aza-dC) restore INHA expression in methylated cancers, suppressing proliferation .
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In prostate cancer, INHA silencing is linked to poor differentiation, highlighting its role as a therapeutic target .
Genetic and Epigenetic Regulation
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Promoter Methylation: Hypermethylation of the INHA promoter suppresses transcription in 47% of melanomas and 60% of leukemias, reversible by 5-Aza-dC treatment .
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LOH and Mutations: Loss of heterozygosity (LOH) at chromosome 2q is frequent in ACC, correlating with reduced inhibin alpha expression .
In Vitro Studies
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Knockdown of INHA in bovine theca cells reduces androgen production by 85% and downregulates CYP17A1 and INSL3 .
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BMPs (2, 4, 6, 7) suppress thecal INHA expression by >90%, countered by exogenous inhibin .
Key Properties and Applications
Product Specs
Q&A
Basic Research Questions
What experimental approaches best characterize inhibin α subunit structure-function relationships in vitro?
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Use co-immunoprecipitation assays to study heterodimer formation with βA/βB subunits .
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Employ X-ray crystallography or cryo-EM to resolve the disulfide bond topology between α and β subunits .
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Validate structural models using site-directed mutagenesis paired with activin receptor binding assays .
How do researchers reliably detect inhibin α in human tissue samples?
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IHC protocols: Use monoclonal antibodies like clone R1 (validated in ovary, testis, and placenta) . Optimize antigen retrieval with Tris/EDTA pH 9.0 for formalin-fixed tissues .
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Quantitative methods: Combine ELISA (for circulating levels) with RT-qPCR targeting INHA mRNA . Include β-actin as a housekeeping control.
What cell lines are appropriate for studying inhibin α’s endocrine regulation?
Advanced Research Challenges
How to resolve contradictions in inhibin α mRNA-protein expression correlations?
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Case example: In 5-AzaC-treated leukemia cells, α-subunit mRNA increased in lymphoid cells but protein levels rose more in myeloid lines .
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Methodological adjustments:
What mechanisms explain tissue-specific roles of inhibin α in cancer?
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Leukemia: Promoter hypermethylation silences INHA, but demethylation via 5-AzaC restores apoptosis via p16 and Tjp1 pathways .
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Reproductive cancers: In ovarian theca cells, INHA knockdown reduces CYP17A1 and androgen synthesis, implicating α-subunit in steroidogenic feedback .
How to design studies isolating inhibin α’s direct vs. indirect effects?
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Transcriptomics: Profile 5-AzaC-treated cells using RNA-seq to identify co-regulated genes (e.g., Dhh, Kitl) .
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Conditional knockout models: Use Cre-lox systems to delete INHA in specific cell lineages (e.g., Sertoli vs. Leydig cells) .
Methodological Troubleshooting
Why do methylation status and protein levels sometimes discord in leukemia cells?
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Secondary epigenetic modifiers (e.g., histone deacetylation) may block translation despite demethylation .
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Validate with combined 5-AzaC/TSA (trichostatin A) treatments and ChIP-seq for H3K27ac marks .
How to address cross-reactivity in inhibin α immunoassays?
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Pre-adsorb antibodies with activin βA/βB subunits to eliminate heterodimer interference .
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Confirm specificity using INHA CRISPR-KO cell lines as negative controls .
Key Data Contradictions in Current Literature
Product Science Overview
Inhibin-Alpha A Chain is a crucial component of the inhibin protein, which plays a significant role in the regulation of the reproductive system. Inhibins are dimeric glycoproteins belonging to the transforming growth factor-beta (TGF-β) superfamily. They are composed of an alpha (α) subunit and one of two beta (β) subunits, either βA or βB, forming inhibin A (α-βA) or inhibin B (α-βB) respectively . The primary function of inhibin is to inhibit the secretion of follicle-stimulating hormone (FSH) from the pituitary gland, thereby regulating the reproductive processes .
The recombinant human Inhibin-Alpha A Chain is typically produced using an expression system in E. coli or Chinese Hamster Ovary (CHO) cells . The process involves the following steps:
- Gene Cloning: The gene encoding the Inhibin-Alpha A Chain is cloned into an appropriate expression vector.
- Transformation: The vector is introduced into the host cells (E. coli or CHO cells) through a process called transformation.
- Expression: The host cells are cultured under conditions that induce the expression of the Inhibin-Alpha A Chain.
- Purification: The expressed protein is purified using chromatographic techniques to achieve a purity of over 95% . The purification process often includes steps such as affinity chromatography, ion-exchange chromatography, and size-exclusion chromatography.
- Formulation: The purified protein is formulated in a suitable buffer, often containing Tris HCl, EDTA, and glycerol, to ensure stability and prevent degradation .
Inhibin-Alpha A Chain participates in various biochemical reactions, primarily involving its interaction with the beta subunits to form inhibin A or inhibin B . These interactions are crucial for its biological activity, including the inhibition of FSH secretion and the regulation of gonadal stromal cell proliferation . The protein undergoes post-translational modifications, such as glycosylation, which are essential for its stability and function .
Inhibin-Alpha A Chain also plays a role in the regulation of activin signaling. Activins are related proteins that stimulate FSH secretion, and inhibins act as antagonists to activins, thereby modulating their effects . The balance between inhibin and activin is critical for maintaining reproductive health and function.
