9.B.198.2.7
GRAMD1C or Aster-C of 662 aas and 1 very hydrophobic TMS at residue 570, near the C-terminus as well as possibly 1 (small peak of hydrophobicity) at the C-terminus. In lipid-poor conditions, it localizes to the ER membrane, and in response to excess cholesterol in the plasma membrane (PM), it is recruited to the endoplasmic reticulum-plasma membrane contact sites (EPCS). This process is mediated by the GRAM domain. At the EPCS, the sterol-binding VASt/ASTER domain binds to cholesterol in the PM and facilitates its transfer from the PM to the ER.The GRAMDs form homo- and hetero-meric complexes to sense the levels of cholesterol in the PM and regulate transport of accessible PM cholesterol to the ER in order to maintain cholesterol homeostasis (Naito and Saheki 2021). GRAMD1C is reported to be a cholesterol transport protein (Charsou et al. 2023).