LAMP2 antibody and other autophagy markers: why flux needs a degradation block

Making an autophagy readout interpretable

1. Know which compartment each marker is in. A lysosomal membrane protein marks the lysosome, not the autophagosome, and its colocalisation with an autophagosome marker is what reports fusion. Treating a lysosomal marker as an autophagy readout confuses the destination with the process.
2. Block degradation, or the result is ambiguous. Every marker downstream of autophagosome formation accumulates when degradation is blocked. The experiment therefore runs with and without a lysosomal inhibitor, and the difference between the two arms is flux. An experiment with one arm cannot distinguish more autophagy from less degradation.
3. Read cargo receptors as turnover. Receptors that link cargo to the autophagosome are themselves degraded, so their level falls when autophagy runs and rises when it is blocked. That inversion catches people out and is exactly why the inhibitor arm matters.
4. Count granules and puncta, not intensity. Stress granule and autophagosome markers concentrate into discrete structures, so the readout is number and size per cell over time. Total intensity averages the structure away and reports very little.
5. Include a known inducer and a known inhibitor. Starvation or a pharmacological inducer produces the expected change, and an inhibitor removes it. Those two arms demonstrate that the assay detects the pathway at all, which a treated-and-untreated pair does not.

Imaging against blotting for this pathway

A blot gives a population average of the marker forms and is the standard flux measurement. Imaging counts structures per cell and shows heterogeneity, which is frequently the real result because autophagy responses are rarely uniform across a culture.

Colocalisation between an autophagosome and a lysosomal marker is the fusion readout and needs chromatic correction and a non-colocalising control pair before any coefficient is quoted.

Buying and validating

Prefer clones with published images in your cell type, and for a multi-year study prefer recombinant reagents that will not vary between lots. Record catalogue number, lot and dilution with every experiment.

Validate with a genetic negative where one exists for the pathway component. For this pathway, knockout lines are widely available and settle specificity far better than an isotype control.

An atf6 antibody and a factor cleaved to become active

ATF6 is held in the endoplasmic reticulum membrane and is cleaved on stress so its amino terminal fragment enters the nucleus, which means an atf6 antibody reports activation by the appearance of a smaller band and by nuclear staining. A clone against the wrong end sees only the full protein. A stress inducing treatment with a stated time is the control that produces the fragment.

A perk antibody and a kinase read by its substrate

PERK autophosphorylates on stress and then phosphorylates eIF2 alpha, so a perk antibody for total protein is a denominator and the informative measurements are its own phosphorylation and its substrate's. The protein is large and membrane associated, so the preparation matters. A time course is necessary because the response adapts, and a late sample can look like no response at all.

A keap1 antibody and the sensor that holds NRF2 down

KEAP1 targets NRF2 for degradation until it is modified by an electrophile, so a keap1 antibody reports the sensor while the readout of the pathway is NRF2 stabilisation and its target genes. KEAP1's own level changes little, which is why a figure resting on it alone says little. It is cysteine rich and sensitive to the reducing agent in the sample buffer, which changes its migration.

An nqo1 antibody and a target gene used as a readout

NQO1 is one of the genes NRF2 switches on, so an nqo1 antibody is used as a pathway output rather than as a subject, and induction over an untreated control is the measurement. A common polymorphism produces an unstable protein, so a cell line may read low for a genetic reason rather than a signalling one, which is worth knowing before a line is called unresponsive.

A kdel antibody and a motif rather than a protein

A kdel antibody recognises a retention motif shared by several endoplasmic reticulum resident chaperones, so it reports a compartment rather than one protein and shows several bands by design. That makes it a convenient marker and a poor choice where a single chaperone is the subject. The motif is at the carboxy terminus, so a tagged construct can hide it and read as absent.

A foxo3a antibody and what its localisation means

A foxo3a antibody reports a stress responsive transcription factor whose information is in where it is rather than how much there is, since it moves between cytoplasm and nucleus on phosphorylation. A phospho specific clone beside the total one is what makes that readable, and both belong on the same blot.

Common questions

Does a LAMP-2 antibody measure autophagy?

No. It marks the lysosome, which is where autophagosomes deliver cargo. Its colocalisation with an autophagosome marker reports fusion; on its own it reports lysosomal abundance.

Why do I need a lysosomal inhibitor arm?

Because every downstream marker accumulates both when more autophagy happens and when degradation is blocked. The difference between the inhibited and uninhibited arms is flux, and a single arm cannot distinguish the two causes.

Why did my NBR1 antibody signal go up when I induced autophagy?

Cargo receptors are degraded along with their cargo, so their level falls with active autophagy and rises when it is blocked. If it rose, either the pathway is blocked or the inducer did not work, and the control arms tell you which.

How should stress granules stained with a G3BP1 antibody be quantified?

As number and size per cell, with a time course after a known stressor. They form and dissolve on a timescale of minutes to tens of minutes, so a single time point can easily sit before or after the peak.

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