Product details
Synonyms = phosphoserine aminotransferase 1,EPIP,NLS2,PSA,PSAT,PSATD
Antibody type = Recombinant Rabbit monoclonal / IgG
Clone = HMV331
Positive control = Kidney: A moderate to strong cytoplasmic and nuclear PSAT1 staining must be seen in a fraction of tubulus cells.
Negative control = Lymph node: Lymphocytes should be PSAT1 negative.
Cellular localization =Intracellular
Reactivity = Human
Application = Immunohistochemistry
Dilution = 1:100 – 1:200
Intended Use = Research Use Only
Relevance of Antibody
PSAT1 is a rate limiting enzyme for glycine synthesis.
Biology Behind
Phosphoserine aminotransferase 1 (PSAT1) is coded by the PSAT1 gene at chromosome 9q21.2. It is a pivotal enzyme to produce serine and α-ketoglutarate, two critical metabolites for both carbon metabolism and the tricarboxylic acid cycle. PSAT1 is a rate limiting enzyme in the serine-glycine synthesis pathway which produces glycine, an essential nutrient for proliferating normal and neoplastic cells. Multiple studies have suggested that PSAT1 overexpression causes increased tumor cell proliferation, tumor progression, and poor patient prognosis in several different cancer types. Germ line PSAT1 mutations are among the causes for serine deficiency disorders which constitute inherited metabolic diseases with a broad phenotypic spectrum including the Neu–Laxova syndrome. In normal tissues, PSAT1 is mainly expressed in the brain, the kidney, and the pancreas but it also occurs in other cell types. Among tumors, PSAT1 expression is most often seen in brain, ovarian and endometrial carcinomas, although PSAT1 expression can also occur in tumors of various other organs.
Staining Pattern in Normal Tissues
Images describing the PSAT1 staining pattern in normal tissues obtained by the antibody HMV331 are shown in our “Normal Tissue Gallery”.
Brain | Cerebrum | Strong, nuclear and cytoplasmic PSAT1 staining of astrocytes. |
Cerebellum | Nuclear and cytoplasmic PSAT1 staining is particularly strong in a subset of glial cells between the molecular and the granule cell layer. | |
Endocrine Tissues | Thyroid | Negative. |
Parathyroid | Weak to moderate, predominantly cytoplasmic PSAT1 staining of a small subset of cells (not in all samples). | |
Adrenal gland | Weak to moderate, predominantly cytoplasmic PSAT1 staining of a subset of cells. | |
Pituitary gland | Strong, predominantly cytoplasmic PSAT1 staining of a small subset of epithelial cells in the anterior lobe. | |
Respiratory system | Respiratory epithelium | Negative. |
Lung | Negative. | |
Gastrointestinal Tract | Salivary glands | Cytoplasmic and nuclear PSAT1 staining of variable intensity can occur in serous glandular cells |
Esophagus | Moderate, nuclear and cytoplasmic PSAT1 staining of the basal cell layer of the epidermis. | |
Stomach | Weak cytoplasmic and nuclear PSAT1 staining of some glandular cells. | |
Duodenum | Distinct cytoplasmic and nuclear PSAT1 staining of some Brunner gland cells and of crypt cells of the duodenal mucosa. | |
Small intestine | Distict cytoplasmic and nuclear PSAT1 staining of few crypt cells. | |
Appendix | Distinct cytoplasmic and nuclear PSAT1 staining of few crypt cells. | |
Colon | Distinct cytoplasmic and nuclear PSAT1 staining of few crypt cells. | |
Rectum | Distinct cytoplasmic and nuclear PSAT1 staining of few crypt cells. | |
Liver | Weak, predominantly cytoplasmic PSAT1 staining of hepatocytes. | |
Gallbladder | Negative. | |
Pancreas | Cytoplasmic and nuclear PSAT1 staining of variable intensity of a subset of acinar cells. Islet cells are PSAT1 negative. | |
Genitourinary | Kidney | Predominantly cytoplasmic PSAT1 staining of variable intensity in most tubuli. |
Urothelium | A strong, granular cytoplasmic PSAT1 staining can occur in urothelial cells (probably due to cross-reactivity). | |
Male genital | Prostate | Negative. |
Seminal vesicles | Negative. | |
Testis | Weak to moderate cytoplasmic PSAT1 staining of Sertoli cells. | |
Epididymis | Weak to moderate cytoplasmic and nuclear PSAT1 staining of chief cells can occur (not in all samples). | |
Female genital | Breast | Negative. |
Uterus, myometrium | Negative. | |
Uterus, ectocervix | Negative. | |
Uterus endocervix | Negative. | |
Uterus, endometrium | Weak to moderate cytoplasmic and nuclear PSAT1 staining of few epithelial cells (not in all samples). | |
Fallopian Tube | Weak cytoplasmic and nuclear PSAT1 staining of a subset of cells. | |
Ovary | Negative. | |
Placenta early | Negative. | |
Placenta mature | Negative. | |
Amnion | Negative. | |
Chorion | Negative. | |
Skin | Epidermis | Variable, faint to moderate, cytoplasmic and nuclear PSAT1 staining of the epidermis, especially in basal and suprabasal cell layers. |
Sebaceous glands | Glands are negative. Moderate, cytoplasmic and nuclear PSAT1 staining of hair follicles. | |
Muscle/connective tissue | Heart muscle | Negative. |
Skeletal muscle | Negative. | |
Smooth muscle | Negative. | |
Vessel walls | Negative. | |
Fat | Negative. | |
Stroma | Negative. | |
Endothelium | Negative. | |
Bone marrow/ lymphoid tissue | Bone marrow | Negative. |
Lymph node | Negative. | |
Spleen | Negative. | |
Thymus | Distinct nuclear and cytoplasmic PSAT1 staining of thymic epithelial cells. | |
Tonsil | Negative. | |
Remarks |
These findings are largely consistent with the RNA data described in the Human Protein Atlas (Tissue expression PSAT1).
Positive control = Kidney: A moderate to strong cytoplasmic and nuclear PSAT1 staining must be seen in a fraction of tubulus cells.
Negative control = Lymph node: Lymphocytes should be PSAT1 negative.
Staining Pattern in Relevant Tumor Types
PSAT1 is most often expressed in brain, ovarian and endometrium carcinomas, but PSAT1 expression can also occur in tumors of various other organs.
The TCGA findings on PSAT1 RNA expression in different tumor categories have been summarized in the Human Protein Atlas.
Compatibility of Antibodies
No data available at the moment
Protocol Recommendations
IHC users have different preferences on how the stains should look like. Some prefer high staining intensity of the target stain and even accept some background. Others favor absolute specificity and lighter target stains. Factors that invariably lead to more intense staining include higher concentration of the antibody and visualization tools, longer incubation time, higher temperature during incubation, higher temperature and longer duration of the heat induced epitope retrieval (slide pretreatment). The impact of the pH during slide pretreatment has variable effects and depends on the antibody and the target protein.
All images and data shown here and in our image galleries are obtained by the manual protocol described below. Other protocols resulting in equivalent staining are described as well.
Manual protocol
Freshly cut sections should be used (less than 10 days between cutting and staining). Heat-induced antigen retrieval for 5 minutes in an autoclave at 121°C in pH 7,8 Target Retrieval Solution buffer. Apply HMV331 at a dilution of 1:200 at 37°C for 60 minutes. Visualization of bound antibody by the EnVision Kit (Dako, Agilent) according to the manufacturer’s directions.
Potential Research Applications
- The diagnostic and prognostic relevance of PSAT1 IHC in tumors and in preneoplastic disease is unresolved.
- The function of PSAT1 in cancer cells is unknown.
- PSAT1 may represent a therapeutic target, at least in tumors with p53-72Pro variant.
Evidence for Antibody Specificity in IHC
There are two ways how the specificity of antibodies can be documented for immunohistochemistry on formalin fixed tissues. These are: 1. Comparison with a second independent method for target expression measurement across a large number of different tissue types (orthogonal strategy), and 2. Comparison with one or several independent antibodies for the same target and showing that all positive staining results are also seen with other antibodies for the same target (independent antibody strategy).
Orthogonal validation: For the antibody HMV331, specificity is supported by the strong concordance with RNA expression data derived from three independent RNA screening studies, including the Human Protein Atlas (HPA) RNA-seq tissue dataset, the FANTOM5 project, and the Genotype-Tissue Expression (GTEx) project, which are all summarized in the Human Protein Atlas (Tissue expression PSAT1). A PSAT1 staining was observed in all organs with a significant PSAT1 RNA expression (Brain, esophagus, salivary gland, liver, adrenal gland, pituitary gland, parathyroid gland, stomach, pancreas, kidney, epididymis, testis, fallopian tube, skin, thymus), except the thyroid. Among PSAT1 RNA negative tissues, immunostaining by HMV331 was not seen in gallbladder, lung, and the bone marrow while small subset of crypt cells in the intestine, few endometrial glands, and urothelial cells stained positive.
Comparison of antibodies: True expression of PSAT1 in most cell types found to be PSAT1 positive by HMV331 is corroborated by a confirmation of these staining’s by another commercially available independent antibody (termed “validation antibody”). This especially applies to cell types from organs that were considered PSAT1 RNA negative such small subset of crypt cells in the intestine and few endometrial glands. As the granular cytoplasmic staining of urothelial cells could not be confirmed by the validation antibody, we consider this staining an antibody specific cross-reactivity of HMV331. Independence of the validation antibody is documented by various stainings (gallbladder epithelium, muscle lymphatic tissues, stomach epithelium) that were only observed by the validation antibody but not by HMV331. These stainings represent antibody specific cross-reactivities of the validation antibody.