ATP DEPLETION ALTERS MYOSIN I-BETA CELLULAR LOCATION IN LLC-PK1 CELLS

The brush border (BB) of the proximal tubule cell (PTC) requires dynam ic membrane events for function. The actin cytoskeleton is necessary f or structure and function in this region. ATP depletion disrupts both structure and function. In this report, myosin I beta location in LLC- PK1 cells was followed during ATP depletion and repletion using immuno fluorescence and Western blot techniques. Myosin I beta colocalized wi th F-actin in the microvilli and cell periphery, but no colocalization was observed with stress fibers. ATP depletion increased the apical F -actin, and myosin I beta was colocalized there. In addition, after AT P depletion, myosin I beta was extracted less by Triton X-100. These c hanges were reversed after ATP repletion. Finally, immunofluorescence of kidney sections shows myosin I beta in the BB. These results place this motor in a dynamic region of the PTC where its actin and membrane binding domains can contribute to PTC function.