The endoplasmic reticulum (ER) is a dynamic organelle central to many essen
tial cellular functions. It is an important calcium store, which functions
in cellular signal transduction cascades. It is also the site of entry for
secreted proteins into the secretory pathway. Lumenal enzymes will fold and
glycosylate these proteins, and if a protein is destined to be secreted, i
t will be packaged into membrane vesicles that bud off from the ER. The ER
is also the site where most cellular lipids are synthesized, It is contiguo
us with the nuclear envelope, which serves as a diffusion barrier to contro
l entry into and out of the nucleus. In the life cycle of a cell, the ER is
in a constant flux of membrane traffic. What maintains the ER in the shape
of an intact reticulum among this constant flux of material? We discuss th
e mechanisms that contribute to the biogenesis of the ER, the maintenance o
f the organelle, as well as processes that give the ER its characteristic s
hape and pattern of inheritance.