A XXXX -sensitive casein kinase I alpha associates with synaptic vesicles and phosphorylates a subset of vesicle proteins.

@entity35 @entity30395 @entity1078 @entity2383
In interphase cells, alpha-casein kinase I (alpha-CKI) is found associated with cytosolic @entity2383 , the centrosome, and within the nucleus. To identify the specific @entity2383 with which alpha-CKI is associated, established cell lines and primary @entity35 neurons were immunofluorescently labeled with an antibody raised to alpha-CKI. In nonneuronal cells, alpha-CKI colocalizes with @entity2383 which align with microtubules and are partially coincident with both Golgi and endoplasmic reticulum markers. In neurons, alpha-CKI colocalizes with synaptic vesicle markers. When synaptic vesicles were purified from @entity35 brain, they were highly enriched in a CKI, based on activity and immunoreactivity. The synaptic vesicle-associated CKI is an extrinsic kinase and was eluted from synaptic vesicles and purified. This purified CKI has properties most similar to alpha-CKI. When the activities of casein kinase I or II were specifically inhibited on isolated synaptic vesicles, CKI was shown to phosphorylate a specific subset of vesicle proteins, one of which was identified as the synaptic vesicle-specific protein @entity30395 . As with alpha-CKI, the synaptic vesicle CKI is inhibited by @entity1078 (PIP2). However, synthesis of PIP2 was detected only in plasma membrane-containing fractions. Therefore, PIP2 may spatially regulate CKI. Since PIP2 synthesis is required for secretion, this inhibition of CKI may be important for the regulation of secretion.
