AKT1S1 Antibody

Basic Research Questions

• What is AKT1S1 and why is it important in cell signaling research?

  AKT1S1 (also known as PRAS40) is a proline-rich substrate of the kinase AKT1 that functions as a negative regulator of the mechanistic target of rapamycin complex 1 (mTORC1). This protein plays crucial roles in multiple cellular processes including:

  • Neuroprotection mediated by nerve growth factor (NGF) after transient focal cerebral ischemia

  • Regulation of cell growth and cell cycle progression

  • Negative regulation of autophagy

  • Mediating insulin signaling to mTOR

  AKT1S1 becomes phosphorylated in response to insulin treatment, which promotes its interaction with 14-3-3 proteins and relieves its inhibitory activity on mTORC1 .

• What are the recommended applications for AKT1S1 antibodies?

  AKT1S1 antibodies have been validated for multiple research applications:

  Application	Recommended Dilution	Notes
  Western Blot (WB)	1:500-1:2000	Detects bands at ~40-68 kDa depending on modifications
  Immunohistochemistry (IHC)	1:100-1:300	Validated in brain tissue samples
  Immunofluorescence (IF)	1:50-1:200	Provides subcellular localization information
  ELISA	1:5000	For quantitative analysis
  Immunoprecipitation (IP)	Per manufacturer	Used for interactome studies

  When selecting an application, researchers should perform optimization using positive and negative controls to determine ideal conditions for their specific experimental system .

• How should AKT1S1 antibodies be stored and handled to maintain reactivity?

  For optimal performance and longevity:

  • Store antibodies at −20°C for up to one year from date of receipt

  • For short-term storage (up to three months), 4°C is acceptable

  • Avoid repeated freeze-thaw cycles

  • Some formulations contain 50% glycerol, 0.5% BSA, and 0.02% sodium azide in PBS

  • Working dilutions should be prepared immediately before use

  Following these storage guidelines helps maintain antibody activity and specificity, particularly important for phospho-specific AKT1S1 antibodies that may be more sensitive to degradation .

Advanced Research Questions

• What methodological approaches can be used to study AKT1S1 interactome changes during cell cycle progression?

  To investigate AKT1S1 interactome dynamics across cell cycle stages:

  1. Cell synchronization techniques:

     • Serum starvation (G0 arrest)

     • Aphidicolin treatment (G1/S arrest)

     • Nocodazole treatment (G2/M arrest)

  2. Verification of cell cycle arrest:

     • Flow cytometry with propidium iodide staining

     • Western blot analysis of cell cycle markers

  3. Interactome analysis:

     • Affinity purification coupled with mass spectrometry (AP-MS)

     • SILAC labeling to distinguish protein associations across cell cycle stages

     • Co-immunoprecipitation followed by western blot for targeted validation

  Studies have identified 213 interacting partners of AKT1S1, with 32 showing dynamic association patterns across cell cycle stages. These interactions can be validated through reverse co-immunoprecipitations using antibodies against suspected interacting proteins .

• How can I differentiate between phosphorylated and non-phosphorylated forms of AKT1S1 in my experiments?

  Several approaches can be employed:

  1. Phospho-specific antibodies:

     • Use antibodies specifically targeting phosphorylated epitopes (e.g., Phospho-Thr246)

     • These antibodies are generated through affinity chromatography using phosphopeptides and negative preadsorption against non-phosphopeptides

  2. Treatment controls:

     • Positive controls: Stimulate cells with insulin, IGF-1, or PDGF to induce phosphorylation

     • Negative controls: Use PI3K/Akt inhibitors to prevent phosphorylation

  3. Lambda phosphatase treatment:

     • Treat sample aliquots with lambda phosphatase to remove phosphate groups

     • Compare migration patterns with untreated samples on Western blots

  4. Differentiation by molecular weight:

     • Phosphorylated AKT1S1 may show a slight mobility shift compared to unphosphorylated form

     • The calculated molecular weight of AKT1S1 is 27.4 kDa, but observed weight is typically 40-68 kDa due to post-translational modifications

• What experimental approaches can elucidate the functional relationship between AKT1S1 and cell cycle regulation?

  Research indicates AKT1S1 influences cell cycle progression through interaction with specific proteins. To investigate this:

  1. RNAi-mediated silencing:

     • Use SMARTpool ON-TARGET plus siRNAs (25-50 nM) targeting AKT1S1 or its interactors

     • Measure effects on population doubling time (PDT) and residence times (RT) in different cell cycle phases

  2. Cell cycle analysis:

     • Quantify DNA content by propidium iodide staining and flow cytometry

     • Calculate residence times in each cell cycle phase

  3. Interactor manipulation:

     • Silence specific G1/S-specific interactors using siRNA

     • Measure effects on PDT and G1 phase residence time

  Studies have identified both facilitating and restricting proteins within the AKT1S1 interactome that influence cell cycle progression. For example:

  Protein	Effect on G1 Phase RT	Effect on PDT	Function
  EPPK1	-9.16h (54% reduction)	-12h (45% reduction)	Restricts G1 progression
  NUCKS1	-5.46h (32% reduction)	-3.15h (12% reduction)	Restricts G1 progression
  EIF2A	+7.99h (47% increase)	+15.6h (59% increase)	Facilitates G1 progression
  MYH9	+4.66h (28% increase)	+7.2h (27% increase)	Facilitates G1 progression

  These counteracting effects suggest AKT1S1 coordinates cell cycle progression with cell growth .

• What controls should be included when validating a new AKT1S1 antibody?

  Comprehensive validation should include:

  1. Specificity controls:

     • Positive control: Human, mouse, or rat cell lysates known to express AKT1S1

     • Negative control: Knockout cell line (e.g., AKT1S1 knockout HeLa)

     • Isoform specificity: Test against recombinant AKT1S1 and related proteins

  2. Application-specific controls:

     • For WB: Molecular weight ladder, loading control (e.g., GAPDH)

     • For IHC/IF: Secondary antibody only, isotype control

     • For phospho-specific antibodies: Treatment with phosphatase

  3. Cross-reactivity assessment:

     • If the antibody claims multi-species reactivity, test on lysates from each species

     • Verify sequence homology between species at the immunogen region

  4. Blocking peptide:

     • Using the immunogenic peptide to compete for antibody binding

     • Should eliminate specific signal if antibody is truly specific

  Researchers should also be aware that AKT1S1 exists in at least three isoforms, which may appear at different molecular weights on Western blots .

• How does AKT1S1 phosphorylation status affect its interaction with mTORC1, and how can this be studied?

  AKT1S1 phosphorylation regulates its inhibitory effect on mTORC1:

  1. Phosphorylation mechanisms:

     • Phosphorylation by AKT1 at Thr246 in response to insulin promotes AKT1S1 interaction with 14-3-3 proteins

     • Phosphorylation by mTOR creates a feedback loop that relieves inhibition

     • Phosphorylation by DYRK3 at Thr246 relieves inhibitory function on mTORC1

  2. Experimental approaches:

     • Phosphomimetic mutants: Generate T246D mutants (mimics phosphorylation)

     • Phospho-dead mutants: Generate T246A mutants (prevents phosphorylation)

     • Proximity ligation assays: Visualize protein-protein interactions in situ

     • FRET-based assays: Measure dynamic interactions in live cells

  3. Assessing downstream effects:

     • Monitor mTORC1 activity through phosphorylation status of S6K1 and 4E-BP1

     • Evaluate effects on protein synthesis using puromycin incorporation assays

     • Measure autophagy induction via LC3-II/LC3-I ratio and p62 levels

  Research suggests a dual regulatory mechanism where AKT1S1 functions as both a substrate and regulator of mTOR, with phosphorylation status determining whether it inhibits or promotes mTORC1 activity .

• What experimental design considerations are important when studying AKT1S1 in different tissue contexts?

  When investigating AKT1S1 across tissue types:

  1. Antibody selection:

     • Verify reactivity in target species (human, mouse, rat)

     • Select antibodies validated for your specific application and tissue type

     • Consider polyclonal antibodies for detection and monoclonal for specific epitopes

  2. Tissue-specific considerations:

     • Brain tissue: AKT1S1 has been implicated in neuroprotection after ischemia; use perfusion fixation for optimal preservation

     • Cancer cell lines: Different expression levels may require adjusted antibody dilutions; compare with normal tissue counterparts

     • Metabolic tissues: Fasting/feeding status affects phosphorylation state

  3. Controls for tissue studies:

     • Use tissues from AKT1S1 knockout animals when available

     • Include both positive (known to express AKT1S1) and negative control tissues

     • For phospho-specific detection, include tissues from animals treated with PI3K/Akt inhibitors

  4. Technical considerations:

     • For brain samples in IHC/IF: Background autofluorescence may require additional blocking steps

     • For Western blot: Tissue-specific extraction buffers may be required for optimal results

     • For comparative studies: Standardize tissue collection, fixation and processing protocols

• How can AKT1S1 antibodies be used to investigate the cross-talk between PI3K/Akt and mTOR signaling pathways?

  To study pathway cross-talk:

  1. Sequential immunoprecipitation approach:

     • First IP with anti-AKT1S1 antibody

     • Followed by western blot analysis for pathway components (Akt, mTOR, Raptor)

     • Or elute and perform second IP with anti-mTOR antibody

  2. Phospho-protein profiling:

     • Treat cells with pathway-specific inhibitors:

       • PI3K inhibitors (LY294002, wortmannin)

       • Akt inhibitors (MK-2206)

       • mTOR inhibitors (rapamycin, Torin1)

     • Analyze phosphorylation status of AKT1S1 and downstream targets

  3. Time-course experiments:

     • Stimulate cells with insulin, IGF-1 or serum

     • Collect samples at multiple timepoints (0-60 minutes)

     • Analyze the temporal relationship between Akt activation, AKT1S1 phosphorylation, and mTORC1 activation

  4. Reconstitution experiments:

     • Silence endogenous AKT1S1 using siRNA

     • Reconstitute with wild-type or phospho-mutant versions

     • Assess effects on both Akt and mTOR signaling outputs

  Research has demonstrated that insulin stimulates protein synthesis and cell growth via Akt phosphorylation of AKT1S1, which relieves its inhibitory effect on mTORC1, highlighting the importance of AKT1S1 as a critical node connecting these two signaling pathways .