PMC

Representative images showing kinetics of granules with displacement <0.5 μm for each condition. Motility of granules with short displacement (those for which the distance between the coordinates at the beginning and the end of the analysis was <0.5 μm) was restricted significantly after LPS treatment in WT cells but not in Munc13-4-deficient neutrophils. Also, the average speed of motion-restricted granules was decreased significantly after LPS treatment in WT cells but not in Munc13-4-deficient neutrophils []. The diameter of the circles depicted represents 0.5 μm. This research was published originally in ref. []. Tg, Transgenic.

The small GTPase Rab27a recruits the effector JFC1 to secretory organelles. JFC1 interacts with the RhoA-GAP GMIP through its C2B domain [], but whether this interaction is sufficient to recruit GMIP to secretory organelles is still obscure. RhoA localizes at azurophilic granules, and GMIP down-regulation induces RhoA activation and increases actin polymerization []. Down-regulation of GMIP or JFC1 increases granule entrapment in cortical actin and decreases exocytosis, while inhibition of the RhoA-downstream signaling pathway has the opposite effect []. In the absence of Rab27, JFC1, or GMIP, secretion is impaired.