September 4, 2012

Membranes are not just cute little jackets that cells wear to keep them protected. Membranes are no joke—they are dynamic hotspots of action, and their composition plays a key role in many cellular processes. Today’s image is from a paper describing the composition of a cell’s plasma membrane during cell morphogenesis.

The cell’s plasma membrane serves as the entryway and exit for material and plays an important role in cell signaling. Although all plasma membranes are made of a bilayer of lipids, those lipids can vary depending on the type of cell. The local composition of lipids in the plasma membrane can affect cellular processes, as seen in the human pathogenic fungus human C. albicans. C. albicans can grow using a filamentous protrusion called a hypha, which was recently found to have an asymmetric distribution of lipids. According to Vernay and colleagues, the growth of the hyphal filament was accompanied by a gradient of the phospholipid PI(4,5)P2 (phosphoinositide bis-phosphate). PI(4,5)P2 is frequently found within membranes at the sites of polarized growth, trafficking, and actin reorganization. Vernay and colleagues found that the sharp gradient of PI(4,5)P2 is essential for proper cell morphogenesis of C. albicans, and depends on the actin cytoskeleton and PI(4)P synthesis. In the images above, hyphal filaments show a gradient of PI(4,5)P2 using a color-coding of PI(4,5)P2 signal (key shows relative levels). Highest PI(4,5)P2 levels are seen at the tips of the filaments.

Aurélia Vernay, Sébastien Schaub, Isabelle Guillas, Martine Bassilana, & Robert A. Arkowitz (2012). A steep phosphoinositide bis-phosphate gradient forms during fungal filamentous growth originally published in the Journal of Cell Biology, 198 (4), 711-730 DOI: 10.1083/jcb.201203099