Time-Resolved FT-IR Microspectroscopy of Protein Aggregation Induced by Heat-Shock in Live Cells

Maintaining the correct folding of cellular
proteins is essential for preserving cellular homeostasis. Protein
dishomeostasis, aberrant protein folding, and protein aggrega-
tion are indeed involved in several diseases including cancer,
aging-associated, and neurodegenerative disorders. Accumu-
lation of protein aggregates can also be induced from a variety
of stressful conditions, such as temperature increase or
oxidative stress. In this work, we monitored by Fourier
transform-infrared (FT-IR) microspectroscopy the response of
live breast cancer MCF-7 and mammary breast adenocarcino-
ma MDA-MB 231 cell lines to severe heat-shock (HS), caused
by the rise of the cellular medium temperature from 37 ± 0.5
°C to 42 ± 0.5 °C. Through the study of the time-evolution of
the second derivatives of the spectra and by the 2D correlation
analysis of FT-IR absorbance data, we were able to identify a common sudden heat-shock response (HSR) among the two cell lines. The hyperfluidization of mammalian cell membranes, the transient increment of the signal lipids, as well as the alteration of proteome profile were all monitored within the first 40 min of stress application, while the persistent intracellular accumulation of extended β-folded protein aggregates was detected after 40 min up to 2 h. As a whole, this paper offers a further prove of the diagnostic capabilities of FT-IR microspectroscopy for monitoring in real-time the biochemical rearrangements undergone by live cells upon external stimulation.