Regulation of cell cycle progression by XXXX /calmodulin-dependent pathways.

@entity1 @entity375 @entity5 @entity14940 @entity460 @entity563 @entity141 @entity1889
Many hormones, growth factors, and cytokines regulate proliferation of their target cells. Perhaps the most universal signaling cascades required for proliferative responses are those initiated by transient rises in intracellular @entity460 ( @entity141 ). The major intracellular receptor for @entity141 is calmodulin (CaM). CaM is a small protein that contains four EF-hand @entity141 binding sites and is highly conserved among eukaryotes. In all organisms in which the CaM gene has been deleted, it is essential. Although @entity141 /CaM is required for proliferation in both unicellular and multicellular eukaryotes, the essential targets of @entity141 /CaM-dependent pathways required for cell proliferation remain elusive. Potential @entity141 /CaM-dependent targets include the @entity563 / @entity1889 phosphatase calcineurin and the family of multifunctional @entity141 /CaM-dependent protein kinases. Whereas these enzymes are essential in @entity14940 , they are not required under normal growth conditions in @entity375 . However, in @entity1 cells, studies demonstrate that both types of enzymes contribute to the regulation of cell cycle progression. Unfortunately, the mechanism by which @entity141 /CaM and its downstream targets, particularly calcineurin and the @entity141 /CaM-dependent protein kinases, regulate key cell cycle-regulatory proteins, remains enigmatic. By understanding how @entity141 /CaM regulates cell cycle progression in normal @entity1 cells, we may gain insight into how hormones control cell division and how @entity5 cells subvert the need for @entity141 and its downstream targets to proliferate.
