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← Theoretical 2

Q69 — Mechanosensitive Ion Channels — OSCA vs Piezo1

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Cell Signaling & Communication

Mechanically activated channels (MA) transfer physical force into electrical current. Piezo1 is a well-characterized subtype of the MA channel. OSCA proteins have been described as sensing receptors that exist not only in mammals but various other eukaryotes like plants and flies. In order to understand the role of OSCA proteins to different stimuli, cells were treated with hyperosmolarity and cell stretching, and the electrical response was recorded. Cells expressing different OSCA variants, OSCA1.1 and OSCA1.2, were compared with Piezo1, in their electrical response, in the figure below.

Two-panel figure. Panel a: patch-clamp recordings of peak current (Imax, in picoamps) for OSCA1.1- and OSCA1.2-expressing cells under isotonic conditions, then hyperosmotic conditions (620 mmol/kg), then isotonic again; each line connects the same cell across the three conditions, and both channels show a modest rise in current under hyperosmolarity. Panel b: peak current (Imax, in nanoamps) for Mock cells and cells expressing mPIEZO1, OSCA1.1, or OSCA1.2 in response to mechanical stretching; Mock cells show near-zero current, while mPIEZO1, OSCA1.1, and OSCA1.2 all show currents in the low-nanoamp range, each significantly above Mock. Figure 1. Left half (panel a): response to hyperosmolarity, recorded in picoamps. Right half (panel b): response to mechanical stretch stimuli, recorded in nanoamps, by patch-clamp recording. Imax is the current peak. Mock cells do not express any of these proteins, while PIEZO1, OSCA1.1 and OSCA1.2 cells were transfected to express the corresponding protein. Lines connect biological replicates.

Use the information and figures to determine whether the statements are true or false.

A. In plants, the MA channels can play a role in adaptation of the roots to the soil environment and gravity.
B. OSCA-expressing cells respond to hyperosmolarity less intensely, as compared to mechanical stimuli.
C. OSCA-expressing cells have a similar response to mechanical stimuli as Piezo1 expressing cells.
D. From the graphs, we can conclude that OSCA 1.2 protein has no role in sensing mechanical stimuli.
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)