Requirement of Adaptor Protein GULP during Stabilin-2-mediated Cell Corpse Engulfment

Abstract

The prompt clearance of cells undergoing apoptosis is critical during embryonic development and normal tissue turnover, as well as during inflammation and autoimmune responses. We recently demonstrated that stabilin-2 is a phosphatidylserine receptor that mediates the clearance of apoptotic cells, thereby releasing the anti-inflammatory cytokine, transforming growth factor-␤. However, the downstream signaling components of stabilin-2-mediated phagocytosis are not known. Here, we provide evidence that the adaptor protein, GULP, physically and functionally interacts with the stabilin-2 cytoplasmic tail. Using fluorescent resonance energy transfer analysis and biochemical approaches, we show that GULP directly binds to the cytoplasmic tail of stabilin-2. Knockdown of endogenous GULP expression significantly decreased stabilin-2-mediated phagocytosis. Conversely, overexpression of GULP caused an increase in aged cell engulfment. The phosphotyrosine binding (PTB) domain of GULP was sufficient for the interaction with stabilin-2; therefore, transduction of TAT fusion PTB domain acts as a dominant negative, resulting in impaired engulfment of aged red blood cells in stabilin-2 expressing cells. In addition, the PTB domain of GULP was able to specifically interact with the NPXY motif of the stabilin-2 cytoplasmic tail. Taken together, these results indicate that GULP is a likely downstream molecule in the stabilin-2-mediated signaling pathway and plays an important role in stabilin-2-mediated phagocytosis.

CD300b regulates the phagocytosis of apoptotic cells via phosphatidylserine recognition

“…43 Stabilin2-mediated uptake of apoptotic cells requires the adaptor molecule, GULP. 44 Our findings demonstrate that CD300b alone can not only tether apoptotic cells, but can mediate efferocytosis when associated with the adaptor molecule, DAP12. Importantly, our results showed that CD300b promotes phagocytosis of apoptotic cells, 45 or avb3 and CD36, 46 can cooperate to enhance efferocytosis.…”

Signalling Pathway Involving GULP, MAPK and Rac1 for SR-BI-Induced Phagocytosis of Apoptotic Cells

“…Besides SR-BI, several PS-recognizing phagocytosis receptors have been identified. Kim and colleagues reported that like SR-BI, PS-bound stabilin-2 binds to GULP and transmits a signal for the induction of phagocytosis (21,35). In contrast, another PS receptor BAI1 binds to the mammalian homologue of CED-12 and transmits a signal for phagocytosis via the mammalian homologue of CED-5 and Rac1 (36).…”

“…The region covering nucleotide positions 348-1019, with the first nucleotide for the translation start codon numbered as 1, of mouse GULP cDNA placed in front of the T7 promoter was synthesized by PCR, and the GULP sequence was transcribed in vitro and processed by dicer (21). siRNA containing a sequence of green fluorescence protein was similarly generated.…”

Do not let death do us part: ‘find-me’ signals in communication between dying cells and the phagocytes

“…12 Stabilin-2 has been reported to require the adapter protein GULP and thymosinβ 4 to engulf apoptotic cells. 19,20 Once internalized, phagolysosome maturation occurs through the action of several Rab-family GTPases eventually leading to the degradation of the ingested cell corpse. 21 'Find-me' signals Both non-professional phagocytes and resident professional phagocytes can clear dying cells under homeostatic conditions.…”