Structure of Transmembrane Domain of Lysosome-associated Membrane Protein Type 2a (LAMP-2A) Reveals Key Features for Substrate Specificity in Chaperone-mediated Autophagy

Abstract

Background: Lysosome-associated membrane protein type 2a (LAMP-2A) is the receptor for chaperone-mediated autophagy (CMA). Results: The transmembrane of LAMP-2A forms a coiled coil helix trimer in n-dodecylphosphocholine (DPC) micelle, and protein substrates interact with its cytosolic tail. Conclusion: Protein substrates and chaperone recognize the same site with equal affinity. Significance: Substrate recognition and recruitment are coupled in CMA.

Structural Basis and Functional Role of Intramembrane Trimerization of the Fas/CD95 Death Receptor

“…This trimeric structure is important for the ability of Fas to induce cell death, explaining the disease phenotypes of Fas-TM mutations. The mode of Fas-TM assembly is entirely different from TM helix dimers formed around the GxxxG sequence motif (Russ and Engelman, 2000), the more common coiled-coil assembly of TM helices that form higher order oligomers (Oxenoid and Chou, 2005; Rout et al, 2014; Wang et al, 2009), and the relatively non-specific, cation-mediated trimeric and tetrameric intermediates of the DAP12 TM domain (Knoblich et al, 2015). The unique structural feature implies the existence of a sequence determinant for the trimeric assembly of Fas-TM.…”

Autophagy: A double-edged sword in intervertebral disk degeneration

“…In chaperone-mediated autophagy, substrate proteins containing a consensus pentapeptide motif (KFERQ) are recognized by a cytosolic chaperone, heat shock cognate protein of 70 kDa (HSC70), which A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 6 subsequently delivers them to the surface of lysosomes [48,49]. These substrate proteins are translocated into the lysosomal lumen through interaction with lysosome-associated membrane protein type-2A (LAMP2A) for degradation [50,51].…”

Hsp90 regulates autophagy and plays a role in cancer therapy

“…Ulk1 plays a central role in the autophagy pathway by receiving signals from upstream modulators such as mTOR and relaying them to its downstream substrates [13]. LAMP-2A is a key regulator of chaperone-mediated autophagy together with a complex of chaperones [14]. Indeed, our primary studies show that silencing of Hsp90 significantly influences the expression of MAPLC3 in Hela cells (data not shown).…”

“…CMA is maximally activated in response to stressors such as prolonged starvation and oxidative stress [38][39][40]. A LAMP-2A, the transmembrane protein component for protein translocation to the lysosome, contains a transmembrane region, a glycosylated luminal region and a cytosolic tail [14,41]. LAMP-2A proteins take part in lysosomal motility along microtubules and protect the lysosomal membrane against degradation [42,43].…”