Counting compartments rather than measuring flux: why a lamp1 antibody, and the lamp-1 antibody and lamp 1 antibody spellings beside it, marks a membrane rather than a degradative capacity and why a generic lysosome marker antibody is a weaker choice, what an lc3 antibody and an lc3b antibody report only when read as a ratio with an inhibitor, how an sqstm1 antibody and a p62 antibody are the same cargo receptor under two names, what a beclin-1 antibody or beclin 1 antibody, an atg5 antibody, an atg7 antibody and an atg16l1 antibody report about machinery rather than activity, where a tfeb antibody reports transcriptional control by moving, what a cathepsin b antibody, a cathepsin d antibody and a cathepsin k antibody measure as zymogen and mature forms, how an npc1 antibody, a lamp-2 antibody, a galc antibody and a pikfyve antibody sit in lysosomal function, and what a rab5 antibody, a rab5a antibody, a rab7 antibody, a vcp antibody and a chmp4b antibody mark along the endosomal route

Measuring flux honestly

1. Always run the inhibitor arm. The interpretable measurement is the difference between marker levels with and without a lysosomal inhibitor. A single measurement without that comparison cannot distinguish increased synthesis of autophagosomes from blocked clearance.
2. Read the lipidated form as a ratio. The informative quantity is the proportion of the marker in its membrane bound form, and it needs a gel that resolves the two species cleanly. Reporting only the lipidated band is a common and misleading shortcut.
3. Use the cargo receptor as the second axis. A receptor that is itself degraded by the pathway falls when flux increases and accumulates when it is blocked. Read in the opposite direction to the membrane marker, it constrains the interpretation considerably.
4. Treat machinery levels as capacity, not activity. Core machinery proteins are present whether or not the pathway is running. Their levels report capacity, and reading them as activity is one of the most frequent errors in this literature.
5. Distinguish zymogen from mature protease. Lysosomal proteases are made as inactive precursors and matured in the compartment. A reagent detecting both reports synthesis; only the mature band reports delivery to a functioning lysosome.

Two readings, opposite conclusions

This is the field where a single blot most reliably produces the wrong answer. Accumulation of a marker is consistent with the pathway running harder and with the pathway being blocked, and the papers that get this wrong are numerous enough that reviewers now ask for the inhibitor arm by default.

Design it in from the start. It doubles the number of lanes and removes the only serious objection to the result.

Imaging adds what blots cannot

Puncta counts per cell, colocalisation between an autophagosome marker and a lysosomal one, and tandem fluorescent reporters that change colour on acidification all report flux more directly than a blot.

Where the conclusion is central, pair a blot with one imaging readout. Two independent methods agreeing is what makes a flux claim durable.

Common questions

Does more autophagosome marker mean more autophagy?

Not on its own. It can equally mean autophagosomes are accumulating because they are not being cleared. The inhibitor comparison is what distinguishes induction from blockade, and no single measurement substitutes for it.

Is a membrane marker a measure of lysosome function?

No. It counts compartments carrying that membrane protein. Function requires acidification and active proteases, which are measured with pH sensitive probes and by looking at protease maturation.

Why does the cargo receptor go the other way?

Because it is degraded along with the cargo it binds. Falling receptor with rising membrane marker indicates flux; both rising together indicates a block.

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