Stomatin-like Protein-1 Interacts with Stomatin and Is Targeted to Late Endosomes

Abstract

The human stomatin-like protein-1 (SLP-1) is a membrane protein with a characteristic bipartite structure containing a stomatin domain and a sterol carrier protein-2 (SCP-2) domain. This structure suggests a role for SLP-1 in sterol/lipid transfer and transport. Because SLP-1 has not been investigated, we first studied the molecular and cell biological characteristics of the expressed protein. We show here that SLP-1 localizes to the late endosomal compartment, like stomatin. Unlike stomatin, SLP-1 does not localize to the plasma membrane. Overexpression of SLP-1 leads to the redistribution of stomatin from the plasma membrane to late endosomes suggesting a complex formation between these proteins. We found that the targeting of SLP-1 to late endosomes is caused by a GYXX⌽ (⌽ being a bulky, hydrophobic amino acid) sorting signal at the N terminus. Mutation of this signal results in plasma membrane localization. SLP-1 and stomatin co-localize in the late endosomal compartment, they co-immunoprecipitate, thus showing a direct interaction, and they associate with detergent-resistant membranes. In accordance with the proposed lipid transfer function, we show that, under conditions of blocked cholesterol efflux from late endosomes, SLP-1 induces the formation of enlarged, cholesterolfilled, weakly LAMP-2-positive, acidic vesicles in the perinuclear region. This massive cholesterol accumulation clearly depends on the SCP-2 domain of SLP-1, suggesting a role for this domain in cholesterol transfer to late endosomes.

Systematic Screens for Proteins That Interact with the Mucolipidosis Type IV Protein TRPML1

“…STOML1 is an integral membrane protein that had previously been shown to localize to late endosomes/lysosomes [42]. Intriguingly, STOML1 has a lumenal sterol carrier protein-2 (SCP-2) domain.…”

A DLL3-targeted antibody-drug conjugate eradicates high-grade pulmonary neuroendocrine tumor-initiating cells in vivo

“…BacMam is a modified baculovirus that infects mammalian cells and encodes for the constitutive expression of a fusion protein consisting of SLP-1 fused to RFP. Previous reports have demonstrated that SLP-1 is a marker of late endosomal intracellular compartments (43). Cells were harvested, washed, and stained in FSM buffer containing SC16, SC16LD6.5, or control reagents (5 µg/ml) for 30 min at 4°C.…”

Stomatin-like Protein 2 Deficiency in T Cells Is Associated with Altered Mitochondrial Respiration and Defective CD4+ T Cell Responses

“…SLP-2 is tightly associated with the mitochondrial inner membrane (32,33), and other members of the SPFH family have been linked to the organization of various membrane microdomains (26)(27)(28)(29)(30)(31). Therefore, it is plausible to suggest that SLP-2 promotes the compartmentalization of the mitochondrial inner membrane into CL-enriched microdomains.…”

“…Proteins of the SPFH superfamily have been linked to the organization of membrane microdomains (26)(27)(28)(29)(30)(31). Based on this assumption, and because SLP-2 is mostly a mitochondrial protein localized in the intermembrane space (32, 33), we examined if SLP-2 deficiency would alter mitochondrial membrane compartmentalization.…”