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Mg2+-ATP induces filament growth from retinal rod outer segments with disrupted plasma membranes
Abstract:
Mg2+-ATP produces a large decrease in near-IR light scattering when added to suspensions of rod outer segments (ROS) when the plasma membranes have been disrupted by a gentle dialysis procedure. When this process is studied by light microscopy with video-enhanced image contrast, the Mg2+-ATP-dependent signal is seen to be associated with the formation of filaments which extend only from those ROS lacking plasma membranes. Both the IR light scattering signal and filament growth are inhibited by vanadate and DCCD but not by colchicine, colcemid or cytochalasins.
Insights
Magnesium-ATP (Mg2+-ATP) addition to disrupted rod outer segments (ROS) causes filament formation and a decrease in light scattering. This process is inhibited by vanadate and DCCD, suggesting a role for specific molecular interactions in ROS structural changes.
Area of Science:
- Biophysics
- Cell Biology
- Photoreceptor Physiology
Background:
- Rod outer segments (ROS) are specialized photoreceptor cells responsible for vision.
- The structural integrity of ROS is crucial for their function.
- Understanding the molecular mechanisms underlying ROS structural changes is important for visual neuroscience.
Purpose of the Study:
- To investigate the effect of Mg2+-ATP on the structural properties of ROS with disrupted plasma membranes.
- To identify the molecular components and processes involved in Mg2+-ATP-induced structural changes in ROS.
Main Methods:
- Preparation of ROS suspensions with disrupted plasma membranes via gentle dialysis.
- Measurement of near-IR light scattering changes upon Mg2+-ATP addition.
- Video-enhanced contrast light microscopy to visualize structural changes.
- Assessment of inhibitor effects (vanadate, DCCD, colchicine, colcemid, cytochalasins).
Main Results:
- Mg2+-ATP addition caused a significant decrease in near-IR light scattering in disrupted ROS.
- Light microscopy revealed Mg2+-ATP-dependent filament formation extending from ROS lacking plasma membranes.
- Both light scattering and filament growth were inhibited by vanadate and DCCD.
- Colchicine, colcemid, and cytochalasins did not affect the observed phenomena.
Conclusions:
- Mg2+-ATP induces filament formation and alters light scattering properties in ROS with compromised plasma membranes.
- The observed effects are mediated by specific molecular targets sensitive to vanadate and DCCD, but not cytoskeletal inhibitors.
- These findings suggest a novel Mg2+-ATP-dependent structural remodeling process in ROS.