Choosing autophagy and stress response antibodies: what a lamp2 antibody marks that an autophagosome marker does not, how an nbr1 antibody reports cargo receptor turnover, why a g3bp1 antibody is counted as granules, and the flux block every one of these readouts needs

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.

Common questions

Does a lamp2 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 cargo receptor level 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 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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