Table I.
Summary of small GTPases discussed in this review. Mouse models are described, unless otherwise stated. Studies using pharmacological inhibitors or permeabilised platelet systems are not included.
| Effect on granule count/content/secretion |
||||||
|---|---|---|---|---|---|---|
| Protein | Gene | Alpha | Dense | Lysosome | Model | Reference |
| Rab27A | RAB27A | Normal vWF levels, normal P-selectin exposure | Normal count/5HT content | nd | Ashen mouse (Rab27a−/- global) | Barral et al. (2002) |
| Rab27B | RAB27B | Normal P-selectin exposure | Reduced count/5HT content, secretion defect-further impaired in Rab27a/b null | nd | Rab27b−/- (global) | Tolmachova et al. (2007) |
| Rab38 | RAB38 | Normal count, and P-selectin exposure | None detected in Megs or Platelets | Normal count | FHH rat (Rab38−/- due to point mutation in gene ATG start site) | Ninkovic et al. (2008) |
| Rab32 | RAB32 | nd | Biogenesis defect in Megs | nd | Rab32 siRNA (MEG-01 cells) | Ambrosio et al. (2012) |
| Rab38 | RAB38 | nd | Biogenesis defect in Megs | nd | Rab38 siRNA (MEG-01 cells) | Ambrosio et al. (2012) |
| Arf6 | ARF6 | Normal count, decreased fibrinogen content | Normal count and secretion | nd | Arf6flox/flox- PF4-Cre | Huang et al. (2016) |
| RalA | RALA | Normal count, and secretion* | Normal count and secretion† | Normal count and secretion | RalA flox/flox-PF4-Cre | Wersäll et al. (2018) |
| RalB | RALB | Normal count, P-selectin exposure defect* | Normal count and secretion† | Normal count and secretion | RalBflox/flox- PF4-Cre | Wersäll et al. (2018) |
| R-Ras2 | RRAS2 | GPVI-specific secretion defect | GPVI-specific secretion defect | nd | Rras2−/- (global) | Janapati et al. (2018) |
‘*’ P-selectin exposure defect markedly enhanced and ‘†’ mild ATP secretion defect in RalA/B double knockout platelets, ‘nd’ indicates no data available, ‘FHH’ indicates fawn-hooded hypertensive.