CHMP4A: Lysates

CHMP4A (charged MVB protein 4A) is one of the three isoforms of CHMP4, the human equivalent of yeast Snf7 (so CHMP4A is also referred to as hSnf7-1). It is a component of the ESCRT-III (endosomal sorting complex required for transport III) complex. The ESCRT complexes mediate membrane budding away from the cytosol and cleavage of membrane necks (membrane fission) from the cytosolic face; hence, they are key in processes such as the formation of MVBs (multivesicular bodies), enveloped virus budding, and membrane abscission in cytokinesis. Not all types of ESCRT complexes, or proteins within those complexes, are necessary for all of these functions. For instance, research into the requirements of ESCRT-III proteins in HIV-1 budding has revealed that CHMP1 and CHMP3 proteins are not essential for this process; at least one member of each of the CHMP2 and CHMP4 families are required; within these families there is some functional redundancy; within the CHMP4 family, the relative importance and abundance of the isoforms is 4B > 4A > 4C; and the absence of CHMP4A or 4B prevents the budding process from progressing to completion.