Stabilization of MORC2 by estrogen and antiestrogens through GPER1- PRKACA-CMA pathway contributes to estrogen-induced proliferation and endocrine resistance of breast cancer cells.

Abstract

Aberrant activation of estrogen signaling through three ESR (estrogen receptor) subtypes, termed ESR1/ERα, ESR2/ERβ, and GPER1 (G protein-coupled estrogen receptor 1), is implicated in breast cancer pathogenesis and progression. Antiestrogens tamoxifen (TAM) and fulvestrant (FUL) are effective for treatment of ESR1-positive breast tumors, but development of resistance represents a major clinical challenge. However, the molecular mechanisms behind these events remain largely unknown. Here, we report that 17β-estradiol (E2), TAM, and FUL stabilize MORC2 (MORC family CW-type zinc finger 2), an emerging oncoprotein in human cancer, in a GPER1-dependent manner. Mechanistically, GPER1 activates PRKACA (protein kinase cAMP-activated catalytic subunit alpha), which in turn phosphorylates MORC2 at threonine 582 (T582). Phosphorylated MORC2 decreases its interaction with HSPA8 (heat shock protein family A [Hsp70] member 8) and LAMP2A (lysosomal associated membrane protein 2A), two core components of the chaperone-mediated autophagy (CMA) machinery, thus protecting MORC2 from lysosomal degradation by CMA. Functionally, knockdown of MORC2 attenuates E2-induced cell proliferation and enhances cellular sensitivity to TAM and FUL. Moreover, introduction of wild-type MORC2, but not its phosphorylation-lacking mutant (T582A), in MORC2-depleted cells restores resistance to antiestrogens. Clinically, the phosphorylation levels of MORC2 at T582 are elevated in breast tumors from patients undergoing recurrence after TAM treatment. Together, these findings delineate a phosphorylation-dependent mechanism for MORC2 stabilization in response to estrogen and antiestrogens via blocking CMA-mediated lysosomal degradation and uncover a dual role for MORC2 in both estrogen-induced proliferation and resistance to antiestrogen therapies of breast cancer cells.

ABBREVIATIONS:

4-OHT: 4-hydroxytamoxifen; Baf A1: bafilomycin A1; CMA: chaperone-mediated autophagy; E2: 17β-estradiol; ESR: estrogen receptor; FUL: fulvestrant; GPER1: G protein-coupled estrogen receptor 1; HSPA8: heat shock protein family A (Hsp70) member 8; LAMP2A: lysosomal associated membrane protein 2A; MORC2: MORC family CW-type zinc finger 2; PRKACA: protein kinase cAMP-activated catalytic subunit alpha; TAM: tamoxifen; VCL: vinculin.

• Authors: Fan Yang, Hong-Yan Xie, Li-Feng Yang, Lin Zhang, Fang-Lin Zhang, Hong-Yi Liu, Da-Qiang Li, Zhi-Ming Shao
• Journal: Autophagy (Autophagy) Vol. 16 Issue 6 Pg. 1061-1076 (06 2020) ISSN: 1554-8635 [Electronic] United States
• PMID: 32401166 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Estrogen Receptor Modulators
• Estrogens
• GPER1 protein, human
• HSC70 Heat-Shock Proteins
• HSPA8 protein, human
• LAMP2 protein, human
• Lysosomal-Associated Membrane Protein 2
• MORC2 protein, human
• RNA, Small Interfering
• Receptors, Estrogen
• Receptors, G-Protein-Coupled
• Transcription Factors
• Tamoxifen
• Fulvestrant
• Estradiol
• Cyclic AMP-Dependent Protein Kinase Catalytic Subunits
• PRKACA protein, human
• Chymases

Topics

• Autophagy (drug effects)
• Breast Neoplasms (drug therapy, genetics, metabolism, pathology)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Chymases (metabolism)
• Cyclic AMP-Dependent Protein Kinase Catalytic Subunits (metabolism)
• Drug Resistance, Neoplasm
• Estradiol (pharmacology)
• Estrogen Receptor Modulators (pharmacology)
• Estrogens (pharmacology)
• Female
• Fulvestrant (pharmacology)
• HSC70 Heat-Shock Proteins (metabolism)
• Humans
• Immunohistochemistry
• Lysosomal-Associated Membrane Protein 2 (metabolism)
• Lysosomes (drug effects, metabolism)
• Phosphorylation
• Protein Stability
• RNA, Small Interfering
• Receptors, Estrogen (metabolism)
• Receptors, G-Protein-Coupled (metabolism)
• Signal Transduction (drug effects)
• Tamoxifen (pharmacology)
• Transcription Factors (genetics, metabolism)