1. The regulation of plasma membrane protein recycling and polar localization.
The regulation of plasma membrane protein recycling and polar localization. The ADP-ribosylation factor (ARF) GTPase guanine-nucleotide exchange factor (GEF) GNOM plays a key role in the recycling of PIN proteins (orange cylinders) between TGN/EE compartments and basal plasma membrane domains. In addition, regulators such as the Rab-type GTPase BEX5 and the ARF-GEF proteins BEN1 and GNL1 are implicated in PIN trafficking. This process also depends on the activity of the exocyst complex (EC), which is suggested to modulate the exocytic sorting of PINs. PIN targeting to the apical plasma membrane domain has been linked to PIN phosphorylation (p), presumably involving the activity of the AGC3-type protein kinase PINOID (PID), which in turn appears to be under the control of Ca2+ and phosphoinositide signaling. The activity of the PP6 phosphatase antagonizes PID, promoting dephosphorylation and PIN sorting to basal domains. PIN targeting to the plasma membrane is suggested to involve ‘super-polar’ exocytosis, as reflected in the accumulation of PIN protein clusters at polar plasma membrane domains. Lateral diffusion of such protein clusters appears to be slow and depends on as-yet-unidentified crosstalk with cell wall components. For example, Hechtian strands (HS) that bridge the space between the cell and plasma membrane have been suggested to act in this process. Adjacent to polar plasma membrane domains, clathrin-mediated endocytosis enforces internalization of PINs in clathrin-coated vesicles (CCVs), preventing their further diffusion within the plasma membrane.
Christian Luschnig, and Grégory Vert Development 2014;141:
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