Higher actin contractility and cargo-loaded clathrin pits create midplane-peaked apico-basal tension profiles in HeLa cells
The mechanical state of the cell membrane is known to be intricately regulated by the underlying actomyosin cytoskeleton. Past studies, however, indicate cell membranes to be mechanically homogenous. In this paper, through the combination of three techniques - interference reflection microscopy (IRM), optical tweezers (OT), and fluorescence lifetime and super-resolution Stimulated Emission Depletion microscopy (FLIM and STED) we investigated the different regions of the plasma membrane of HeLa cells to understand whether their mechanical state is uniform, noisy, or has gradients. Combining IRM and OT-based tension measurements, we observed a height- dependent tension profile. FLIM measurements revealed a patterned tension axially, instead of a monotonic decrease with height. From STED measurements having ∼40-nm resolution, it was revealed that real overlaps of myosin fibers (length ∼100 nm) with actin followed an apical gradient in their colocalization, implying that contractility could be a greater determinant of the tension profile than membrane-actin linkage. This colocalization was highest in the midplane, identifying this region in having elevated contractility and tension. Interestingly, in the same region, we also found an increased presence of invaginated clathrin coated pits – known in the literature for enhancing cellular tension. Our work lays the foundation for further studies into the origins of contractility gradients and the necessity of patterned heterogeneities in tension, particularly through exploration of functionally different cells. [Cell Reports Physical Science 7, 103046, 2026]
Tanmoy Ghosh, 1,4 Anisha Majhi, 2,4 Avijit Kundu, 2,3 Ayan Banerjee, 2, * and Bidisha Sinha 1, * 1 Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, Nadia 741246, India 2 Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, Nadia 741246, India 3 Present address: Department of Physics, Simon Fraser University, Burnaby, BC V5A 1S6 Canada 4 These authors contributed equally *Email: ayan@iiserkol.ac.in (A.B.), bidisha.sinha@iiserkol.ac.in (B.S.)
#Research Highlight
Posted on: January 25th, 2026