PMID- 37961544
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20240329
DP  - 2023 Oct 23
TI  - Altered Platelet-Megakaryocyte Endocytosis and Trafficking of Albumin and 
      Fibrinogen in RUNX1 Haplodeficiency.
LID - 2023.10.23.23297335 [pii]
LID - 10.1101/2023.10.23.23297335 [doi]
AB  - Platelet alpha-granules have numerous proteins, some synthesized by megakaryocytes 
      (MK) and others not synthesized but incorporated by endocytosis, an incompletely 
      understood process in platelets/MK. Germline RUNX1 haplodeficiency, referred to 
      as familial platelet defect with predisposition to myeloid malignancies (FPDMM), 
      is associated with thrombocytopenia, platelet dysfunction and granule 
      deficiencies. In previous studies, we found that platelet albumin, fibrinogen and 
      IgG levels were decreased in a FPDMM patient. We now show that platelet 
      endocytosis of fluorescent-labeled albumin, fibrinogen and IgG is decreased in 
      the patient and his daughter with FPDMM. In megakaryocytic human erythroleukemia 
      (HEL) cells, siRNA RUNX1 knockdown (KD) increased uptake of these proteins over 
      24 hours compared to control cells, with increases in caveolin-1 and flotillin-1 
      (two independent regulators of clathrin-independent endocytosis), LAMP2 (a 
      lysosomal marker), RAB11 (a marker of recycling endosomes) and IFITM3. Caveolin-1 
      downregulation in RUNX1-deficient HEL cells abrogated the increased uptake of 
      albumin, but not fibrinogen. Albumin, but not fibrinogen, partially colocalized 
      with caveolin-1. RUNX1 knockdown increased colocalization of albumin with 
      flotillin and of fibrinogen with RAB11 suggesting altered trafficking of both. 
      The increased albumin and fibrinogen uptake and levels of caveolin-1, 
      flotillin-1, LAMP2 and IFITM3 were recapitulated by shRNA RUNX1 knockdown in CD34 
      (+) -derived MK. These studies provide the first evidence that in RUNX1- 
      haplodeficiency platelet endocytosis of albumin and fibrinogen is impaired and 
      that megakaryocytes have enhanced endocytosis with defective trafficking leading 
      to loss of these proteins by distinct mechanisms. They provide new insights into 
      mechanisms governing endocytosis and alpha-granule deficiencies in RUNX1- 
      haplodeficiency. KEY POINTS: Platelet content and endocytosis of alpha-granule 
      proteins, albumin, fibrinogen and IgG, are decreased in germline RUNX1 
      haplodeficiency. In RUNX1 -deficient HEL cells and primary MK endocytosis is 
      enhanced with defective trafficking leading to decreased protein levels.
FAU - Carpio-Cano, Fabiola Del
AU  - Carpio-Cano FD
FAU - Mao, Guangfen
AU  - Mao G
FAU - Goldfinger, Lawrence E
AU  - Goldfinger LE
FAU - Wurtzel, Jeremy
AU  - Wurtzel J
FAU - Guan, Liying
AU  - Guan L
FAU - Alam, Afaque Mohammad
AU  - Alam AM
FAU - Lee, Kiwon
AU  - Lee K
FAU - Poncz, Mortimer E
AU  - Poncz ME
FAU - Rao, A Koneti
AU  - Rao AK
AUID- ORCID: 0000-0002-3078-7778
LA  - eng
PT  - Preprint
DEP - 20231023
PL  - United States
TA  - medRxiv
JT  - medRxiv : the preprint server for health sciences
JID - 101767986
UIN - Blood Adv. 2024 Feb 08;:. PMID: 38330198
PMC - PMC10635164
EDAT- 2023/11/14 06:42
MHDA- 2023/11/14 06:43
PMCR- 2023/11/09
CRDT- 2023/11/14 03:59
PHST- 2023/11/14 06:43 [medline]
PHST- 2023/11/14 06:42 [pubmed]
PHST- 2023/11/14 03:59 [entrez]
PHST- 2023/11/09 00:00 [pmc-release]
AID - 2023.10.23.23297335 [pii]
AID - 10.1101/2023.10.23.23297335 [doi]
PST - epublish
SO  - medRxiv [Preprint]. 2023 Oct 23:2023.10.23.23297335. doi: 
      10.1101/2023.10.23.23297335.