Annexin I is phosphorylated in the multivesicular body during the processing of the epidermal growth factor receptor.
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Discussion
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Implication
Experimental study demonstrates annexin I phosphorylation within multivesicular bodies during growth factor receptor processing, indicating a key role in inward membrane vesiculation.
Key Points
- To identify multivesicular body-associated substrates of the epidermal growth factor receptor (EGF-R) kinase that mediate receptor sorting to the lysosome.
- Isolated multivesicular bodies (MVBs) using a density shift technique.
- Assessed in vitro substrate phosphorylation and evaluated calcium-dependent membrane association of annexin I in isolated MVBs and intact cells.
- The EGF-R and annexin I were identified as the primary substrates phosphorylated in vitro within isolated MVBs containing active EGF-R kinase.
- Annexin I associated with plasma membranes and MVBs in a calcium-independent manner, but phosphorylation in isolated MVBs converted it into a calcium-dependent membrane-associated form.
- Cells containing active EGF-R kinase displayed reduced levels of calcium-independent annexin I in MVBs, supporting in vivo phosphorylation-driven conversion.
Cite This Study
Futter et al. (1993) studied this question.