Different NK cell-activating receptors preferentially recruit Rab27a or Munc13-4 to perforin-containing granules for cytotoxicity

Blood. 2009 Nov 5;114(19):4117-27. doi: 10.1182/blood-2009-06-225359. Epub 2009 Aug 24.


The autosomal recessive immunodeficiencies Griscelli syndrome type 2 (GS2) and familial hemophagocytic lymphohistiocytosis type 3 (FHL3) are associated with loss-of-function mutations in RAB27A (encoding Rab27a) and UNC13D (encoding Munc13-4). Munc13-4 deficiency abrogates NK-cell release of perforin-containing lytic granules induced by signals for natural and antibody-dependent cellular cytotoxicity. We demonstrate here that these signals fail to induce degranulation in resting NK cells from Rab27a-deficient patients. In resting NK cells from healthy subjects, endogenous Rab27a and Munc13-4 do not colocalize extensively with perforin. However, phorbol 12-myristate 13-acetate and ionomycin stimulation or conjugation to susceptible target cells induced myosin-dependent colocalization of Rab27a and Munc13-4 with perforin. Unexpectedly, individual engagement of receptors leukocyte functional antigen-1, NKG2D, or 2B4 induced colocalization of Rab27a, but not Munc13-4, with perforin. Conversely, engagement of antibody-dependent cellular cytotoxicity receptor CD16 induced colocalization of Munc13-4, but not Rab27a, with perforin. Furthermore, colocalization of Munc13-4 with perforin was Rab27a-dependent. In conclusion, Rab27a or Munc13-4 recruitment to lytic granules is preferentially regulated by different receptor signals, demonstrating that individual target cell ligands regulate discrete molecular events for lytic granule maturation. The data suggest Rab27a facilitates degranulation at an early step yet highlight a reciprocal relationship between Munc13-4 and Rab27a for degranulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Case-Control Studies
  • Cell Degranulation
  • Child
  • Cytoplasmic Granules / immunology
  • Cytoplasmic Granules / metabolism
  • Cytotoxicity, Immunologic
  • GPI-Linked Proteins
  • Humans
  • In Vitro Techniques
  • Ionomycin / pharmacology
  • Killer Cells, Natural / drug effects
  • Killer Cells, Natural / immunology*
  • Killer Cells, Natural / physiology
  • Lymphocyte Activation
  • Lymphocyte Function-Associated Antigen-1 / metabolism
  • Lymphohistiocytosis, Hemophagocytic / genetics
  • Lymphohistiocytosis, Hemophagocytic / immunology*
  • Lymphohistiocytosis, Hemophagocytic / physiopathology*
  • Membrane Proteins / deficiency*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mutation
  • Perforin / metabolism*
  • Receptors, IgG / metabolism
  • Receptors, Immunologic / metabolism*
  • Signal Transduction
  • Tetradecanoylphorbol Acetate / pharmacology
  • rab GTP-Binding Proteins / deficiency*
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism*
  • rab27 GTP-Binding Proteins


  • FCGR3B protein, human
  • GPI-Linked Proteins
  • Lymphocyte Function-Associated Antigen-1
  • Membrane Proteins
  • Receptors, IgG
  • Receptors, Immunologic
  • UNC13D protein, human
  • rab27 GTP-Binding Proteins
  • Perforin
  • Ionomycin
  • RAB27A protein, human
  • rab GTP-Binding Proteins
  • Tetradecanoylphorbol Acetate